National Polar-orbiting Operational Environmental Satellite System Research Articles

A physical algorithm for precipitable water vapour retrieval over land using passive microwave observations

ABSTRACT Precipitable water vapour (PWV) plays an important role in weather prediction, hydrological cycles and climate change. In this study, a physics-based algorithm was proposed to retrieve PWV over land using satellite passive microwave observations near 165.50 GHz and 183.31 GHz, which have higher spatial resolution and lower sensitivity to land surface emissivity than low-frequency channels. The algorithm uses a perturbation formulation of simplified radiative transfer equation to derive PWV and at-surface brightness temperature (BT) in 165.50 GHz simultaneously. It directly derives the at-surface BT instead of land surface temperature, so the algorithm needs no prior information of surface emissivity. Sensitivity analysis and retrieval experiments from simulated data were carried out for Advanced Technology Microwave Sounder (ATMS) onboard the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) satellite. The results showed that the algorithm using ATMS channels 17, 18 and 19 measurements can significantly reduce the PWV retrieval errors caused by surface emissivity uncertainty. The coefficient of determination (R 2), root-mean-square error (RMSE), and bias of the retrieved PWV from ATMS data by the proposed algorithm and SuomiNet Global Positioning System (GPS) PWV were 0.90, 0.43 cm and −0.02 cm, respectively. In addition, the Visible Infrared Imaging Radiometer Suite (VIIRS) cloud products were used to evaluate the effects of cloud on the PWV retrievals. The results showed that the presence of cloud does not decrease the accuracy of the PWV retrievals.

CHLOROPHYLL-A CONCENTRATIONS ESTIMATION FROM AQUA-MODIS AND VIIRS-NPP SATELLITE SENSORS IN SOUTH JAVA SEA WATERS

This study aimed to estimate the concentration of chlorophyll-a from satellite imagery of National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) in the south Java Sea waters and compare it to the concentrations of chlorophyll-a estimation result from the MODIS-Aqua satellite. NPP satellite had Visible/Infrared Imager Radiometer Suite (VIIRS) sensors which performance was same as Moderate Resolution Imaging Spectroradiometer (MODIS) sensor with a better spatial resolution. This study used daily satellite imagery of VIIRS-NPP for the period of September 2012 to August 2013. The algorithm that was used to estimate the concentration of chlorophyll-a was Ocean Color 3-band ratio (OC-3). The results showed that the spatial distribution pattern of chlorophyll-a concentration between VIIRS - NPP sensor and MODIS had the same pattern, but the estimation of chlorophyll-a concentration from the MODIS sensor was higher than VIIRS -NPP sensor. The concentration of chlorophyll-a showed that there were spatial and temporal variation in the south Java Sea waters. Generally, concentrations of chlorophyll-a was higher in East monsoon than West monsoon.

A comparison between three surface type data sets adopted by the community radiative transfer model

ABSTRACTThe accuracy of simulated radiances for surface-sensitive visible and infrared channels is affected by the specification of surface type. The current version of Community Radiative Transfer Model (CRTM) employs three surface type data sets, which are referred to as the National Polar-orbiting Operational Environmental Satellite System (NPOESS), the U. S. Geological Survey (USGS), and the International Geosphere-Biosphere Programme (IGBP) data sets, respectively. In this study, the consistencies and discrepancies among these three surface type data sets are examined. The surface type is specified consistently among the three data sets in equatorial and polar regions, but not in other regions especially around 60° N. The desert and snow types have the highest consistency among the three surface type data sets. The tundra in the IGBP data set, the needle-leaf forecast and mixed forest in the NPOESS data set, and the mixed forest in the USGS data set have the greatest discrepancy from the other two data sets. Finally, a canonical case is used to demonstrate that the impacts of the three surface type datasets on CRTM simulations are significant, pointing to a need for a rigorously defined surface type data set.

Joint Polar Satellite System: The United States next generation civilian polar‐orbiting environmental satellite system

AbstractNOAA's next generation polar‐orbiting environmental satellite system, designated as the Joint Polar Satellite System (JPSS), was proposed in February 2010, as part of the President's Fiscal Year 2011 budget request, to be the Civilian successor to the restructured National Polar‐Orbiting Operational Environmental Satellite System (NPOESS). Beginning 1 October 2013, the JPSS baseline consists of a suite of five instruments: advanced microwave and infrared sounders critical for short‐ and medium‐range weather forecasting; an advanced visible and infrared imager needed for environmental assessments such as snow/ice cover, droughts, volcanic ash, forest fires and surface temperature; ozone sensor primarily used for global monitoring of ozone and input to weather and climate models; and an Earth radiation budget sensor for monitoring the Earth's energy budget. NASA will fund the Earth radiation budget sensor and the ozone limb sensor for the second JPSS operational satellite—JPSS‐2. JPSS is implemented through a partnership between NOAA and the U.S. National Aeronautics and Space Administration (NASA). NOAA is responsible for overall funding; maintaining the high‐level requirements; establishing international and interagency partnerships; developing the science and algorithms, and user engagement; NOAA also provides product data distribution and archiving of JPSS data. NASA's role is to serve as acquisition Center of Excellence, providing acquisition of instruments, spacecraft and the multimission ground system, and early mission implementation through turnover to NOAA for operations.

Cloudy Forecast for Weather Satellite Data

![Figure][1] NPOESS Preparatory Project satellite (artist's rendition). CREDIT: NOAA IN SPACE COLLECTION In the News Focus story “Weather forecasts slowly clearing up” (9 November, p. [734][2]), R. Kerr nicely summarizes how the growing improvement in prediction is coming from a focus on “more computer power, the assimilation of radar observations, and more physically realistic models.” He emphasizes that better assimilation of satellite data is a key element of improved forecasting. Unfortunately, these potential improvements will have little effect on forecasts if the basic data set from the existing polar-orbiting weather satellite system is not available. In a report issued in June 2012 ([ 1 ][3]), the U.S. Government Accountability Office noted that “data from this system is the predominant input to numerical weather prediction models” and warned that “there will likely be a gap in satellite data lasting 17 to 53 months” when the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project satellite ceases operations and NOAA's new satellite system (the Joint Polar Satellite System) launches. The report also notes that there are “potential satellite data gaps in DOD [Department of Defense] and European polar satellite programs which provide supplementary information to NOAA forecasts.” These gaps are a grave problem and would seriously degrade weather forecasts. Therefore, the agencies responsible for weather forecasting—NOAA, DOD, and NASA—should make filling the polar satellite data gaps the first priority in order to ensure that future forecasts are as good as possible. 1. [↵][4] U.S. GAO, “Polar-orbiting environmental satellites: Changing requirements, technical issues, and looming data gaps require focused attention,” GAO-12-604 (2012); [www.gao.gov/products/GAO-12-604][5]. [1]: pending:yes [2]: /lookup/doi/10.1126/science.338.6108.734 [3]: #ref-1 [4]: #xref-ref-1-1 View reference 1 in text [5]: http://www.gao.gov/products/GAO-12-604

Industry and Government Space Weather Experts Meet

The fifth annual NOAA Space Weather Prediction Center (SWPC)-Commercial Space Weather Interest Group (CSWIG) Summit was held on 28 April 2011 in Boulder, Colo., in association with the 2011 Space Weather Workshop. Interest was high, in the United States and internationally, in potential space weather impacts on many aspects of everyday life because of the increased vulnerability of technological systems and the possibility that a major space weather event may occur as the twenty-fourth solar cycle begins to progress toward solar maximum. Industry and government space weather experts participated in the summit. Devrie Intriligator (Carmel Research Center, Inc.) and W. Kent Tobiska (Space Environment Technologies (SET)) served as cochairs. Tom Bogdan, Director of SWPC, summarized SWPC’s current fiscal situation and future plans. SWPC has been successful in educating members of the executive branch and other government officials about space weather. President Obama’s proposed fiscal year (FY) 2012 budget includes Department of Defense and NOAA funding for the Deep Space Climate Observatory (DSCOVR), the replacement for the Advanced Composition Explorer (ACE) spacecraft, which warns of approaching interplanetary disturbances from the Sun. It is crucial for Congress to appropriate this funding if DSCOVR is to be launched on schedule in 2014. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC-2) mission is also in the proposed FY 2012 budget. Starting in early fall 2011, SWPC is planning to have two forecasters on duty 24 hours a day, 7 days a week. SWPC’s top operational priorities include an improved WangSheeleyArge (WSA) model of the Sun/solar wind interface and a Ground Induced Current regional model. A high priority is improved forecasting of the interplanetary magnetic field characteristics of a coronal mass ejection that hits Earth. David Bouwer (SET) summarized SWPC’s External Space Weather Data Store (E-SWDS) and other data/model sources. E-SWDS is the most reliable data source with the fewest changes/interruptions in service, format, and parameters. CSWIG looks forward to when E-SWDS also will include improved model outputs (e.g., ENLIL, WSA, etc.). Intriligator summarized concerns on the quality and quantity of future data including those from ACE and National Polar-Orbiting Operational Environmental Satellite System (NPOESS) replacements, the Geostationary Operational Environmental Satellite (GOES), etc. Space weather research, operations, and forecasts are data limited, and longterm monitoring of solar, interplanetary, and near-Earth regions is crucial. NOAA is tasked with this monitoring. Stable funding of long-term spacecraft lines (e.g., GOES) is needed. Michael Bonadonna (Office of the Federal Coordinator for Meteorology (OFCM)) updated the group on the National Space Weather Program (NSWP) and OFCM activities. One of the near-term priorities of OFCM is to improve its ability to work with the commercial sector. At present, there is no mechanism for the commercial sector to participate in the NSWP Council or other high-level NSWP activities. The Office of Science and Technology Policy has requested that NSWP assess U.S. space weather capabilities now and 10 years in the future. Tobiska discussed CSWIG participation in software test beds and Small Business Innovative Research opportunities as ways of leveraging funding. He also discussed moving toward space weather common practices and a quality assurance program including standards as developed by the American Institute of Aeronautics and Astronautics (http://spacewx.com, see the “Standards” link under “Resources”). Geoff Crowley (Atmospheric and Space Technology Research Associates) reported on the American Commercial Space Weather Association (ACSWA), the space weather association that was unanimously formed last year at the SWPCCSWIG Summit. The ACSWA executive committee (Crowley, Intriligator, Robert Schunk, and Tobiska) had earlier drafted the mission statement for ACSWA and established a Web site (http://sw01.spaceweather.usu.edu/ACSWA/ landing.html), which was unveiled at the summit meeting. Bonadonna and Bogdan enthusiastically supported ACSWA. Genene Fisher

Automated Lightning Flash Detection in Nighttime Visible Satellite Data

Abstract The Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) nighttime visible channel was designed to detect earth–atmosphere features under conditions of low illumination (e.g., near the solar terminator or via moonlight reflection). However, this sensor also detects visible light emissions from various terrestrial sources (both natural and anthropogenic), including lightning-illuminated thunderstorm tops. This research presents an automated technique for objectively identifying and enhancing the bright steaks associated with lightning flashes, even in the presence of lunar illumination, derived from OLS imagery. A line-directional filter is applied to the data in order to identify lightning strike features and an associated false color imagery product enhances this information while minimizing false alarms. Comparisons of this satellite product to U.S. National Lightning Detection Network (NLDN) data in one case as well as to a lightning mapping array (LMA) in another case demonstrate general consistency to within the expected limits of detection. This algorithm is potentially useful in either finding or confirming electrically active storms anywhere on the globe, particularly those occurring in remote areas where surface-based observations are not available. Additionally, the OLS nighttime visible sensor provides heritage data for examining the potential usefulness of the Visible-Infrared Imager-Radiometer Suite (VIIRS) Day/Night Band (DNB) on future satellites including the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP). The VIIRS DNB will offer several improvements to the legacy OLS nighttime visible channel, including full calibration and collocation with 21 narrowband spectral channels.

Comparing MODIS and AIRS Infrared-Based Cloud Retrievals

AbstractComparisons are described for infrared-derived cloud products retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Atmospheric Infrared Sounder (AIRS) using measured spatial response functions obtained from prelaunch AIRS calibration. One full day (1 January 2005) of global collection-5 MODIS and version-5 AIRS retrievals of cloud-top temperature Tc, effective cloud fraction f, and derived effective brightness temperature Tb,e is investigated. Comparisons of Tb,e demonstrate that MODIS and AIRS are essentially radiatively consistent and that MODIS Tb,e is 0.62 K higher than AIRS Tb,e for all scenes, increasing to 1.43 K for cloud described by AIRS as single layer and decreasing to 0.50 K for two-layer clouds. Somewhat larger differences in Tc and f are observed between the two instruments. The magnitudes of differences depend partly on whether MODIS uses a CO2-slicing or 11-μm brightness temperature window retrieval method. Some cloud- and regime-type differences and similarities between AIRS and MODIS cloud products are traceable to the assumptions made about the number of cloud layers in AIRS and also to the MODIS retrieval method. This (partially) holistic comparison approach should be useful for ongoing algorithm refinements, rigorous assessments of climate applicability, and establishment of the capability of synergistic MODIS and AIRS retrievals for improved cloud quantities and also should be useful for future observations to be made by the National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP).

NPOESS

The United States is merging its two polar-orbiting operational environmental satellite programs operated by the Department of Commerce and the Department of Defense into a single system, which is called the National Polar-orbiting Operational Environmental Satellite System (NPOESS). During the next decade, NPOESS will provide global operational data to meet many of the needs of weather forecasters, climate researchers, and global decision makers for remotely sensed Earth science data and global environmental monitoring. The NPOESS Preparatory Project (NPP) will be launched in 2011 as a precursor to NPOESS to reduce final development risks for NPOESS and to provide continuity of global imaging and atmospheric sounding data from the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) missions. Beginning in 2014, NPOESS spacecraft will be launched into an afternoon orbit and in 2016 into an early-morning orbit to provide significantly improved operational capabilities and benefits to satisfy critical civil and national security requirements for space-based, remotely sensed environmental data. The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Meteorological Operation (MetOp) spacecraft will complement NPOESS in a midmorning orbit. The joint constellation will provide global coverage with a data refresh rate of approximately four hours. NPOESS will observe more phenomena simultaneously from space and deliver a data volume significantly greater than its operational predecessors with substantially improved data delivery to users. Higher-resolution (spatial and spectral) and more accurate imaging and atmospheric sounding data will enable improvements in short- to medium-range weather forecasts. Multispectral and hyperspectral instruments on NPOESS will provide global imagery and sounding products useful to the forecaster that are complementary to those available from geostationary satellites. NPOESS will support the operational needs of meteorological, oceanographic, environmental, climatic, and space environmental remote sensing programs and provide continuity of data for climate researchers. This article that describes NPOESS was completed and accepted for publication prior to the White House decision in February 2010 ordering a major restructuring of the NPOESS program. The Department of Commerce will now assume primary responsibility for the afternoon polar-orbiting operational environmental satellite orbit and the Department of Defense will take primary responsibility for the early morning orbit. However, NPP, as described in this article, is still scheduled to be launched in 2011. Several of the instruments and program elements described in this article are also likely to be carried forward into future U.S. polar-orbiting operational environmental satellite missions.

Differentiating between Clouds and Heavy Aerosols in Sun-Glint Regions

Abstract An approach is presented to distinguish between clouds and heavy aerosols in sun-glint regions with automated cloud classification algorithms developed for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) program. The approach extends the applicability of an algorithm that has already been applied successfully in areas outside the geometric and wind-induced sun-glint areas of the earth over both land and water surfaces. The successful application of this approach to include sun-glint regions requires an accurate cloud phase analysis, which can be degraded, especially in regions of sun glint, because of poorly calibrated radiances of the National Aeronautics and Space Administration (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Consequently, procedures have been developed to replace bad MODIS level 1B (L1B) data, which may result from saturation, dead/noisy detectors, or data dropouts, with radiometrically reliable values to create the Visible Infrared Imager Radiometer Suite (VIIRS) proxy sensor data records (SDRs). Cloud phase analyses produced by the NPOESS VIIRS cloud mask (VCM) algorithm using these modified VIIRS proxy SDRs show excellent agreement with features observed in color composites of MODIS imagery. In addition, the improved logic in the VCM algorithm provides a new capability to differentiate between clouds and heavy aerosols within the sun-glint cone. This ability to differentiate between clouds and heavy aerosols in strong sun-glint regions is demonstrated using MODIS data collected during the recent fires that burned extensive areas in southern Australia. Comparisons between heavy aerosols identified by the VCM algorithm with imagery and heritage data products show the effectiveness of the new procedures using the modified VIIRS proxy SDRs. It is concluded that it is feasible to accurately detect clouds, identify cloud phase, and distinguish between clouds and heavy aerosol using a single cloud mask algorithm, even in extensive sun-glint regions.

IASI spectral radiance validation inter-comparisons: case study assessment from the JAIVEx field campaign

Abstract. Advanced satellite sensors are tasked with improving global-scale measurements of the Earth's atmosphere, clouds, and surface to enable enhancements in weather prediction, climate monitoring, and environmental change detection. Measurement system validation is crucial to achieving this goal and maximizing research and operational utility of resultant data. Field campaigns employing satellite under-flights with well-calibrated Fourier Transform Spectrometer (FTS) sensors aboard high-altitude aircraft are an essential part of this validation task. The National Polar-orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed-Interferometer (NAST-I) has been a fundamental contributor in this area by providing coincident high spectral and spatial resolution observations of infrared spectral radiances along with independently-retrieved geophysical products for comparison with like products from satellite sensors being validated. This manuscript focuses on validating infrared spectral radiance from the Infrared Atmospheric Sounding Interferometer (IASI) through a case study analysis using data obtained during the recent Joint Airborne IASI Validation Experiment (JAIVEx) field campaign. Emphasis is placed upon the benefits achievable from employing airborne interferometers such as the NAST-I since, in addition to IASI radiance calibration performance assessments, cross-validation with other advanced sounders such as the AQUA Atmospheric InfraRed Sounder (AIRS) is enabled.

Third Space Weather Summit Held for Industry and Government Agencies

The potential for space weather effects has been increasing significantly in recent years. For instance, in 2008 airlines flew about 8000 transpolar flights, which experience greater exposure to space weather than nontranspolar flights. This is up from 368 transpolar flights in 2000, and the number of such flights is expected to continue to grow. Transpolar flights are just one example of the diverse technologies susceptible to space weather effects identified by the National Research Council’s Severe Space Weather Events—Understanding Societal and Economic Impacts: A Workshop Report (2008). To discuss issues related to the increasing need for reliable space weather information, experts from industry and government agencies met at the third summit of the Commercial Space Weather Interest Group (CSWIG) and the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center (SWPC), held 30 April 2009 during Space Weather Week (SWW), in Boulder, Colo. Devrie Intriligator (Carmel Research Center, Inc.) and W. Kent Tobiska (Space Environment Technologies (SET)) cochaired the summit. In opening the session, Intriligator praised SWPC and Thomas Bogdan, its director, for implementing CSWIG’s request for External Space Weather Data Store (E-SWDS), a near–real time operational database electronic communication method between SWPC and external core partner users. Bogdan discussed SWPC priorities, goals, and plans. Bogdan said he anticipates that more stable budgets will enable SWPC to continue hardware modernization, hire and train forecasters, and put the ENLIL model into operation. He noted that SWPC is working with NOAA aviation and other core entities on overlapping concerns involving space weather. David Bouwer (SET), who represented CSWIG during the E-SWDS implementation, praised the SWPC staff, summarized E-SWDS’s advantages, and answered questions about E-SWDS. Intriligator raised CSWIG’s concerns about the quality and availability of data, including data from a possible replacement for the Advanced Composition Explorer (ACE) satellite at Lagrange point L1 and from satellites such as National Polar-orbiting Operational Environmental Satellite System (NPOESS), Geostationary Operational Environmental Satellites (GOES), and Defense Meteorological Satellites Program (DMSP). Intriligator stressed that a rapid launch of an L1 replacement is urgently needed because ACE is unable to return reliable real-time solar wind data during space weather events such as the 2003 Halloween storm (NOAA Technical Memorandum OAR SEC-88, “Halloween space weather storms of 2003”). In addition, other ACE instruments, such as its low-energy particle detectors, have suffered degradation. Many space weather forecasts need ACE and other data as inputs. If the crucial real-time input data are not available, the space weather community may not be able to test and validate forecasting models during the upcoming solar maximum. To address this situation, Bogdan discussed two possible options: buying data from a commercial satellite at L1, and an interagency cooperative launch of Deep Space Climate Observatory (DSCOVR), a satellite that NASA has built but not launched due to funding issues. Bogdan also summarized the National Space Weather Program (NSWP) participation in the Committee for Space Environmental Sensor Mitigation Options (CSESMO) with Office of Science and Technology Policy and Office of Management and Budget staff. Michael Bonadonna (Office of the Federal Coordinator for Meteorology) summarized recent NSWP activities, including updating NSWP, determining the scope of CSESMO activities, and organizing the 2009 Space Weather Enterprise Forum. In addition, Bonadonna discussed the 2006 “Report of the Assessment Committee for the National Space Weather Program”

Recent space sensor developments at ABB Analytical for weather forecasting applications

The generation of daily weather forecasts relies to a large extent on the use of data from dedicated satellites. In recent years, several programs have been targeted at improving the sensors providing weather forecast data, both in polar and geostationary orbits. As part of the US National Polar-orbiting Operational Environmental Satellite System (NPOESS), the Cross-track Infrared Sounder (CrIS) is the new generation of sounding instruments providing vertical profiles from polar orbits of atmospheric temperature, pressure, and humidity. ABB Analytical has developed the interferometer module and the internal calibration target for the CrIS sensor. An overview of these contributions is presented. The Hyperspectral Environmental Suite (HES) is meant to be the next generation of US weather sounders from geostationary orbits. In Europe, the Meteosat Third Generation will also make use of an improved infrared sounder, the IRS. ABB Analytical has developed a generic interferometer module suitable for these two p...

A global Bayesian sensitivity analysis of the 1d SimSphere soil–vegetation–atmospheric transfer (SVAT) model using Gaussian model emulation

Sensitivity analysis consists of an integral and important validatory check of a computer simulation model before the code is used in performing any kind of analysis operation. The present paper demonstrates the use of a relatively new method and tool for conducting global sensitivity analysis (GSA) for environmental models, providing simultaneously the first GSA study of the widely used 1d soil–vegetation–atmospheric transfer (SVAT) model named SimSphere. A software platform called the Gaussian emulation machine for sensitivity analysis (GEM SA), which has been developed for performing a GSA via Bayesian theory, is applied to SimSphere model in order to identify the most responsive model inputs to the simulation of key model outputs, detect their interactions and derive absolute sensitivity measures concerning the model structure. This study is also very timely in that, use of this particular SVAT model is currently being considered to be used in a scheme being developed for the operational retrieval of the soil surface moisture content by National Polar-orbiting Operational Environmental Satellite System (NPOESS), in a series of satellite platforms that are due to be launched in the next 12 years starting from 2016. The employed GSA method was found capable of identifying the most responsive SimSphere inputs and also of capturing their key interactions for each of the simulated target quantities on which the GSA was conducted. The most sensitive model inputs were the topography parameters (slope, aspect) as well as the fractional vegetation cover and soil surface moisture availability. The implications of these findings for the future use of SimSphere are discussed.

A Geometry-Based Approach to Identifying Cloud Shadows in the VIIRS Cloud Mask Algorithm for NPOESS

Abstract A geometry-based approach is presented to identify cloud shadows using an automated cloud classification algorithm developed for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) program. These new procedures exploit both the cloud confidence and cloud phase intermediate products generated by the Visible/Infrared Imager/Radiometer Suite (VIIRS) cloud mask (VCM) algorithm. The procedures have been tested and found to accurately detect cloud shadows in global datasets collected by NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) sensor and are applied over both land and ocean background conditions. These new procedures represent a marked departure from those used in the heritage MODIS cloud mask algorithm, which utilizes spectral signatures in an attempt to identify cloud shadows. However, they more closely follow those developed to identify cloud shadows in the MODIS Surface Reflectance (MOD09) data product. Significant differences were necessary in the implementation of the MOD09 procedures to meet NPOESS latency requirements in the VCM algorithm. In this paper, the geometry-based approach used to predict cloud shadows is presented, differences are highlighted between the heritage MOD09 algorithm and new VIIRS cloud shadow algorithm, and results are shown for both these algorithms plus cloud shadows generated by the spectral-based approach. The comparisons show that the geometry-based procedures produce cloud shadows far superior to those predicted with the spectral procedures. In addition, the new VCM procedures predict cloud shadows that agree well with those found in the MOD09 product while significantly reducing the execution time as required to meet the operational time constraints of the NPOESS system.

An Overview of the Use of the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) Model for the Study of Land-Atmosphere Interactions

Soil Vegetation Atmosphere Transfer (SVAT) models consist of deterministic mathematical representations of the physical processes involved between the land surface and the atmosphere and of their interactions, at time-steps acceptable for the study of land surface processes. The present article provides a comprehensive and systematic review of one such SVAT model suitable for use in mesoscale or boundary layer studies, originally developed by [1]. This model, which has evolved significantly both architecturally and functionally since its foundation, has been widely applied in over thirty interdisciplinary science investigations, and it is currently used as a learning resource for students in a number of educational institutes globally. The present review is also regarded as very timely, since a variation of a method using this specific SVAT model along with satellite observations is currently being considered in a scheme being developed for the operational retrieval of soil surface moisture by the US National Polar-orbiting Operational Environmental Satellite System (NPOESS), in a series of satellites that are due to be launched from 2016 onwards.

A review of Ts/VI remote sensing based methods for the retrieval of land surface energy fluxes and soil surface moisture

Imagery from remote sensing systems, often combined with ancillary ground information, is able to provide repetitive, synoptic views of key parameters characterizing land surface interactions, including surface energy fluxes and surface soil moisture. Differing methodologies using a wide range of remote sensing data have been developed for this purpose. Approaches vary from purely empirical to more complex ones, including residual methods and those that have their basis in the biophysical properties characterizing a two-dimensional Ts/VI (surface temperature/ vegetation index) scatterplot domain derived from remote sensing observations. The present article aims to offer a comprehensive and systematic review of this latter group of methods, which differ in terms of the complexity and assumptions they entail as well as their requirement for field-based and other ancillary data. Prior to the review, the biophysical meanings and properties encapsulated in the Ts/VI feature space is elucidated, since these represent the building block upon which all the Ts/VI methods described herein are based. The overview of the Ts/VI methods is also very timely, as one such method is being scheduled in the operational retrieval of surface soil moisture content by the National Polar-orbiting Operational Environmental Satellite System (NPOESS), in a series of satellite platforms due to be launched in the next 12 years starting from 2016.

Creating Proxy VIIRS Data From MODIS: Spectral Transformations for Mid- and Thermal-Infrared Bands

Prior to the launch of a new satellite, simulated sensor data are often desired to develop and test the new sensors and algorithms. Ideally, these data closely approximate the data that will be collected on-orbit. Although radiative-transfer models can be employed for this purpose, all models have biases, and none can completely mimic the complex heterogeneity of Earth's environmental system. An alternative approach is to derive ldquoproxyrdquo data sets by transforming real observations collected from past or current sensors. Proxy data inherently contain both natural Earth radiation characteristics and sensor noise as the data from the new sensor will. In preparation for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) and NPOESS Preparatory Project missions, we developed a methodology to create proxy data for the mid- and thermal-infrared bands of the Visible-Infrared Imager-Radiometer Suite (VIIRS). Specifically, by combining radiative-transfer modeling and data from NASA's Atmospheric Infrared Sounder (AIRS), we developed spectral transformation equations to convert real Moderate Resolution Imaging Spectroradiometer (MODIS) data into proxy VIIRS data. The functional forms of the equations were determined through regression analysis. Typically, the best spectral transformation equation for a given VIIRS band was a function of multiple MODIS bands, sensor/solar geometry, and surface type. All transformation equations are for clear-sky conditions. Our daytime midinfrared transformation equations have an accuracy that is below the predicted sensor noise for all surface types. Our thermal-infrared equations over land are most accurate for vegetated covers; our ocean equations are accurate for most bands. Validation of this approach with the Advanced Very High Resolution Radiometer suggests that this method may provide higher accuracy proxy data than other methods. Although the advantage in using AIRS is its hyperspectral design, allowing simulation of MODIS and VIIRS bands, its coarse spatial resolution presented a disadvantage in identifying pure land-cover and cloud-free pixels for generating the equation coefficients. Our primary intent with this paper is to offer a methodology for consideration by other sensor teams. Our provisional MODIS-to-VIIRS spectral transformation equations are included for some example surface types.

Industry and Government Officials Meet for Space Weather Summit

Commercial airlines, electric power grids, cell phones, handheld Global Positioning Systems: Although the Sun is less active due to solar minimum, the number and types of situations and technologies that can benefit from up-to-date space weather information are growing. To address this, the second annual summit of the Commercial Space Weather Interest Group (CSWIG) and the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center (SWPC) was held on 1 May 2008 during Space Weather Workshop (SWW), in Boulder, Colo. The meeting began with a summary by Thomas Bogdan, director of SWPC, on the progress made on action items from the first annual summit, held in June 2007 (see Space Weather, 5, S10002, doi:10.1029/2007SW000348, 2007). Discussions that ensued related to the continued lack of available sources for solar and other data, the lack of a planned follow-on for the Advanced Composition Explorer (ACE) spacecraft, and the lack of space weather instrumentation on the National Polar-orbiting Operational Environmental Satellite System (NPOESS). CSWIG was especially concerned with the continued lack of knowledge of current SWPC priorities and plans for space weather products. John Kappenman (Metatech Corporation), chair of CSWIG, referred the attendees to the 2006 Report of the Assessment Committee for the National Space Weather Program (http://www.nswp.gov/nswp _acreport0706.pdf), which recommended better coordination between National Space Weather Program (NSWP) agencies and the private sector. Bogdan discussed the status of a planned dedicated server for commercial access, as requested by CSWIG at last year’s summit. Bogdan summarized the challenges facing SWPC, including the lack of availability of key space weather data sets. He anticipates that SWPC will not include some space weather data and products in its core priorities. In light of this, Bogdan said that CSWIG members may be interested in generating for the public the products that SWPC will no longer supply, underscoring that he viewed CSWIG and SWPC as existing in a very important partnership. CSWIG members voiced concerns about the need for advance knowledge of SWPC core priorities so that when CSWIG members develop business plans, the companies do not unintentionally invest in areas where SWPC also plans to commit resources. Mark Gunzelman, then at the Office of the Federal Coordinator of Meteorology (OFCM), which oversees NSWP, spoke about responses to the 2006 Assessment Report and the intent of OFCM to allow the commercial space weather community to actively participate in deliberations of the NSWP Committee. It may be possible to include several members of CSWIG as official representatives and/or technical consultants. Devrie Intriligator (Carmel Research Center) organized and moderated a roundtable session at SWW on behalf of CSWIG. The session’s success in raising appreciation for important space weather issues and the contributions of the commercial sector led Bogdan to announce that such CSWIG roundtables would become permanent features of future SWWs. Summit participants agreed that continued dialogue between CSWIG and SWPC was essential for both commercial and public space weather enterprises. Further, they agreed that another meeting would be held during 2009 SWW and that as-needed teleconferences would be held in the intervening period.

Strategy for studying nocturnal aerosol optical depth using artificial lights

In this concept study, we develop a strategy for the monitoring of nighttime aerosol particle optical properties over land using artificial lights on the earth's surface. We demonstrate the possibility of detecting significant aerosol events and deriving variations in aerosol optical depth using the operational linescan system (OLS) on defence meteorological satellite program (DMSP) platforms. Since the OLS instruments have no on‐board calibration, only a qualitative study of the potential to estimate aerosol and cloud properties using city lights at night is shown in this paper. The technique is demonstrated using China and India as test regions. With the launch of the visible/infrared imager/radiometer suite (VIIRS) instrument on the national polar‐orbiting operational environmental satellite system (NPOESS) in the coming decade, fully quantitative retrieval of nighttime aerosol particle optical properties from space observations using such methods will become possible. Such work will benefit aerosol forecasting, safety of navigation, aerosol data assimilation and climate studies.