Polar-orbiting Operational Environmental Satellite Research Articles

VIIRS Night-Time Light Image in the Spatial Structure Identification of Banyuwangi Regency

A spatial structure is a hierarchical arrangement of settlement centers and a network system of infrastructure and facilities that support the community’s socio-economic activities. Spatial structure is important because the city’s rapid growth requires regional service center planning. In general, the method for determining the spatial structure uses the Centrality Index (IS) with a variable number of facilities, infrastructure, and people to obtain a hierarchical arrangement of regional service centers. However, this method is often constrained by data limitations, so in this study remote sensing technology was used through night light imagery in identifying potential centers. This study used the Visible and Infrared Imaging Radiometer Suite (VIIRS) sensor, one of the sensors carried by the Suomi-NPP (National Polar-orbiting Operational Environmental Satellite System Preparatory Project) satellite. Identification is done by overlaying the night light image with the existing spatial structure to produce potential centers. Based on the analysis results, eight classifications are based on the light emission interval class, where the higher the class, the higher the light emission value, which indicates the potential for a new center. The Pesanggaran sub-district is in class eight, the Tegaldimo sub-district is in class six, and the Banyuwangi sub-district is in class one.

Can We Intercalibrate Satellite Measurements by Means of Data Assimilation? An Attempt on LEO Satellites

AbstractLow Earth Orbit satellites offer extensive data of the radiation belt region, but utilizing these observations is challenging due to potential contamination and difficulty of intercalibration with spacecraft measurements at Highly Elliptic Orbit that can observe all equatorial pitch‐angles. This study introduces a new intercalibration method for satellite measurements of energetic electrons in the radiation belts using a Data assimilation (DA) approach. We demonstrate our technique by intercalibrating the electron flux measurements of the National Oceanic and Atmospheric Administration (NOAA) Polar‐orbiting Operational Environmental Satellites (POES) NOAA‐15,‐16,‐17,‐18,‐19, and MetOp‐02 against Van Allen Probes observations from October 2012 to September 2013. We use a reanalysis of the radiation belts obtained by assimilating Van Allen Probes and Geostationary Operational Environmental Satellites observations into 3‐D Versatile Electron Radiation Belt (VERB‐3D) code simulations via a standard Kalman filter. We compare the reanalysis to the POES data set and estimate the flux ratios at each time, location, and energy. From these ratios, we derive energy and L* dependent recalibration coefficients. To validate our results, we analyze on‐orbit conjunctions between POES and Van Allen Probes. The conjunction recalibration coefficients and the data‐assimilative estimated coefficients show strong agreement, indicating that the differences between POES and Van Allen Probes observations remain within a factor of two. Additionally, the use of DA allows for improved statistics, as the possible comparisons are increased 10‐fold. Data‐assimilative intercalibration of satellite observations is an efficient approach that enables intercalibration of large data sets using short periods of data.

Intercomparison of Landsat OLI and JPSS VIIRS Using a Combination of RadCalNet Sites as a Common Reference

Independent radiometric data collected from multiple ground sites as part of vicarious calibration activities can be combined to harmonize the data products of Earth observation sensors with different temporal, spectral, and spatial resolutions. Recent coordinated international efforts for open fiducial reference measurements have provided the worldwide user community with new ways to explore the calibration and harmonization of data produced by the sensors. To be correct, the results from each ground system must be traceable to the same well-understood standard system, and ideally to the international system of units (SI). Additionally, the calibration test site should be homogeneous over an area larger than the spatial resolutions of each sensor, so that ground measurements are representative of the area seen by the sensors being calibrated. Here, we use a combination of independent and SI-traceable radiometric data provided from two sites of the Radiometric Calibration Network (RadCalNet) to compare the radiometric response of sensors with different spectral and spatial resolutions that operate on different orbits. These sensors are Operational Land Imagers (OLI) of the Landsat-8 and Landsat-9 missions, and Visible Infrared Imaging Radiometer Suites (VIIRS) of the Suomi-National Polar-Orbiting Operational Environmental Satellite System Preparatory Project (SNPP) and Joint Polar Satellite System-1 (JPSS-1) missions. The sensor radiometric responses are compared via temporal averaging of the ratios of top-of-atmosphere reflectance values for each sensor to those reported by RadCalNet. Our intercomparison results show that these on-orbit sensors are calibrated within their absolute radiometric uncertainties. The absolute radiometric uncertainties of single-sensor over single-site intercomparisons at 550 nm is between 5% and 6%. Having the opportunity to look at the intercomparison results of Landsat-9 OLI compared to each calibration site individually and then in combination allowed us to investigate potential systematic site-dependent biases. We did not observe significant site-dependent biases in the behavior of the four on-orbit sensors compared to the calibration sites. The absolute radiometric uncertainty of a single sensor over multiple-site intercomparisons at 550 nm is 5.4%. We further investigated site-dependent biases by looking at the double-ratio calibration coefficients of the on-orbit sensors, calculated with reference to those sites.

Energetic Electron Precipitation via Satellite and Balloon Observations: Their Role in Atmospheric Ionization

Information about the energetic electron precipitation (EEP) from the radiation belt into the atmosphere is important for assessing the ozone variability and dynamics of the middle atmosphere during magnetospheric and geomagnetic disturbances. The accurate values of energetic electron fluxes depending on their energy range are one of the most important problems for calculating atmospheric ionization rates, which, in turn, are taken into account for estimating ozone depletion in chemistry–climate models. Despite the importance of these processes for the high latitudes of middle atmosphere, precipitation of energetic electrons is still insufficiently studied. In order to better understand EEP and related processes in the atmosphere, it is important to have many realistic observations of EEP in order to correctly characterize their spectra. Invading the atmosphere, precipitating energetic electrons, in the range from tens of keV to relativistic energies of more than 1 MeV, generate bremsstrahlung, which penetrates into the stratosphere and is recorded by detectors on balloons. However, these observations can be made only when the balloon is at stratospheric heights. Near-Earth satellites, such as the polar-orbiting operational environmental satellites (POES), are constantly registering precipitating electrons in the loss cone, but are moving too fast in space. Based on a comparison of the results of EEP measurements on balloons and onboard POES satellites in 2003, we propose a criterion that makes it possible to constantly monitor EEP ionization at stratospheric heights using observations on POES satellites.

Northeast China Cold Vortex Observed by FY‐3 MWTS‐2 and MetOp AMSU‐A

AbstractThe northeast China cold vortex (NCCV) refers to a closed low‐pressure system over northeast China extending from China‐Siberia to the northwest Pacific coast region. It is cut off from the westerly jet belt in the middle and upper troposphere, has a cold core, lasts several days, and could bring heavy rain events in late spring and summer that are of great challenge to weather forecasters. This study investigates the possibility of observing temperature structures of NCCVs by two microwave temperature sounders, that is, the Microwave Temperature Sounder‐2 (MWTS‐2) and the Advanced Microwave Sounding Unit‐A (AMSU‐A) onboard the two polar‐orbiting operational environmental satellites (POES) Fenyun‐3 satellite FY‐3D and Meteorological Operational satellite MetOp‐B, respectively. The MWTS‐2 and AMSU‐A together provide 3D atmospheric temperatures in the middle and upper troposphere, as well as the lower stratosphere four times daily. Both limb‐corrected direct observations of brightness temperature and retrievals of atmospheric temperature within NCCVs are characterized by cold and warm cores below and above the tropopause, respectively, comparing favorably with the European Centre for Medium‐Range Weather Forecasts ERA5 reanalysis. Compared with the ERA5 reanalysis in June 2019, the MWTS‐2 retrieved atmospheric temperatures have no scan‐dependent biases, the biases are smaller than ±0.2K, and root‐mean‐square errors (RMSEs) are smaller than and 2.0K at all altitudes. This study suggests the possibility of using multiple POES microwave‐temperature‐sounding observations for near‐real‐time monitoring of NCCVs' 3D temperature structures.

Statistically Determining the Spatial Extent of Relativistic Electron Precipitation Events Using 2‐s Polar‐Orbiting Satellite Data

AbstractRelativistic electron precipitation (REP) from the outer radiation belt into Earth's atmosphere poses risks for satellites and affects Earth's climate, producing ozone‐destroying compounds. Characterizing the spatial extent of REP events, which are periods of precipitation localized in space and time, is important for quantifying these effects and improving understanding of outer radiation belt dynamics, allowing quantification of the relative roles of atmospheric and magnetopause particle loss. Following Shekhar et al. (2017, https://doi.org/10.1002/2017JA024716), who used 16 s resolution data from particle detectors onboard NOAA's Polar‐orbiting Operational Environmental Satellites (POES) and the ESA's Meterological Operational (MetOp) Satellites, we work to more precisely determine the spatial extent of REP events using higher‐resolution (2 s) data from the same instruments. We algorithmically search through 6 years of data (October 2012 to December 2018) from a maximum of seven simultaneously orbiting satellites, identifying REP events and determining their start and end times and locations. We find that the majority of events are highly localized spatially and, unlike Shekhar et al. (2017, https://doi.org/10.1002/2017JA024716), we do not observe a cluster of broad events around midnight magnetic local time (MLT). Based on case studies, we suggest that this discrepancy results from the differences in data resolution, indicating that the broad regions of precipitation around midnight MLT identified by Shekhar et al. (2017, https://doi.org/10.1002/2017JA024716) may be composed of several adjacent but narrowly confined regions of precipitation, potentially with independent causes. Additional work is necessary to further classify events and identify their likely mechanisms.

Odd hydrogen response thresholds for indication of solar proton and electron impact in the mesosphere and stratosphere

Abstract. Understanding the atmospheric forcing from energetic particle precipitation (EPP) is important for climate simulations on decadal time scales. However, presently there are large uncertainties in energy flux measurements of electron precipitation. One approach to narrowing these uncertainties is by analyses of EPP direct atmospheric impacts and their relation to measured EPP fluxes. Here we use observations from the microwave limb sounder (MLS) and Whole Atmosphere Community Climate Model (WACCM) simulations, together with EPP fluxes from the Geostationary Operational Environmental Satellite (GOES) and Polar-orbiting Operational Environmental Satellite (POES) to determine the OH and HO2 response thresholds to solar proton events (SPEs) and radiation belt electron (RBE) precipitation. Because of their better signal-to-noise ratio and extended altitude range, we utilize MLS HO2 data from an improved offline processing instead of the standard operational product. We consider a range of altitudes in the middle atmosphere and all magnetic latitudes from pole to pole. We find that the nighttime flux limits for day-to-day EPP impact detection using OH and HO2 are 50–130 protonscm-2s-1sr-1 (E>10 MeV) and 1.0–2.5×104 electronscm-2s-1sr-1 (E = 100–300 keV). Based on the WACCM simulations, nighttime OH and HO2 are good EPP indicators in the polar regions and provide best coverage in altitude and latitude. Due to larger background concentrations, daytime detection requires larger EPP fluxes and is possible in the mesosphere only. SPE detection is easier than RBE detection because a wider range of polar latitudes is affected, i.e., the SPE impact is rather uniform poleward of 60∘, while the RBE impact is focused at 60∘. Altitude-wise, the SPE and RBE detection are possible at ≈ 35–80 and ≈ 65–75 km, respectively. We also find that the MLS OH observations indicate a clear nighttime response to SPE and RBE in the mesosphere, similar to the simulations. However, the MLS OH data are too noisy for response detection in the stratosphere below 50 km, and the HO2 measurements are overall too noisy for confident EPP detection on a day-to-day basis.

Using ecosystem service supply and ecosystem sensitivity to identify landscape ecology security patterns in the Lanzhou-Xining urban agglomeration, China

The construction of an ecological security pattern (ESP) is an important way to ensure regional ecological security and to achieve sustainable regional development. It is also one of the hotspot topics of landscape ecology research. This paper identifies the ecological source through the evaluation of the ecosystem service and ecosystem sensitivity of the Lanzhou-Xining (Lan-Xi) urban agglomeration. The minimum cumulative resistance (MCR) model modified by night light data NPP/VIIRS (National Polar-orbiting Operational Environmental Satellite System Preparatory Project/Visible Infrared Imaging Radiometer Suite) was used to measure the relative resistance of the materials and energy circulation between the source areas, and to establish the resistance surface of the ecological source area expansion. Then ecological corridors were identified based on ecological sources and resistance surface. The ecological strategic node is the ecological fragile point in the ecological corridors. The ecological strategic node is identified with hydrological module by superimposing the “ridge line” of cumulative ecological resistance with the ecological corridor. Combined with ecological sources, corridors and strategic nodes, the ESP of the Lan-Xi urban agglomeration can be constructed. The ecological source of the Lan-Xi urban agglomeration accounts for 28.42% of the total area, most of which is distributed within Qinghai Province. The nature reserves in the area are all located within the ecological source area. A total of 41 potential ecological corridors have been identified in the study area. The total length of the potential corridors is 1201.03 km, comprising 23 source corridors and 18 radiation corridors. There are 30 strategic nodes identified in the Lan-Xi urban agglomeration. These locations are the most vulnerable areas of the ecological corridors. Ecological engineering should be applied in the construction of corridors. Affected by the ecological source, the potential ecological corridor extends from the northwest to the southeast, which is basically consistent with the direction trend of the mountains in the region.

Spatial Distributions of Nitric Oxide in the Antarctic Wintertime Middle Atmosphere During Geomagnetic Storms

AbstractEnergetic electron precipitation leads to increased nitric oxide (NO) production in the mesosphere and lower thermosphere. NO distributions in the wintertime, high‐latitude Southern Hemisphere atmosphere during geomagnetic storms are investigated. NO partial columns in the upper mesosphere at altitudes 70–90 km and in the lower thermosphere at 90–110 km have been derived from observations made by the Solar Occultation For Ice Experiment (SOFIE) on board the Aeronomy of Ice in the Mesosphere (AIM) satellite. The SOFIE NO measurements during 17 geomagnetic storms in 2008–2014 have been binned into selected geomagnetic latitude and geographic latitude/longitude ranges. The regions above Antarctica showing the largest instantaneous NO increases coincide with high fluxes of 30–300 keV precipitating electrons from measurements by the second‐generation Space Environment Monitor (SEM‐2) Medium Energy Proton and Electron Detector (MEPED) instrument on the Polar‐orbiting Operational Environmental Satellites (POES). Significant NO increases over the Antarctic Peninsula are likely due to precipitation of >30 keV electrons from the radiation belt slot region. NO transport is estimated using Horizontal Wind Model (HWM14) calculations. In the upper mesosphere strong eastward winds (daily mean zonal wind speed ~20–30 m s−1 at 80 km) during winter transport NO‐enriched air away from source regions 1–3 days following the storms. Mesospheric winds also introduce NO‐poor air into the source regions, quenching initial NO increases. Higher up, in the lower thermosphere, weaker eastward winds (~5–10 m s−1 at 100 km) are less effective at redistributing NO zonally.

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.

Specifying High‐Altitude Electrons Using Low‐Altitude LEO Systems: The SHELLS Model

AbstractWe describe an artificial neural network model of the near‐Earth space radiation environment. The geomagnetic activity index and low‐earth‐orbit (LEO) electron flux measurements from the National Oceanic and Atmospheric Administration Polar‐orbiting Operational Environmental Satellite (POES) operational spacecraft are used as model training inputs. Electron fluxes from National Aeronautics and Space Administration's Van Allen Probe spacecraft form the training outputs. We demonstrate that the model can accurately specify outer radiation belt ( –7) electron fluxes at two energies, 350 keV and 1 MeV. Various performance metrics are calculated using out‐of‐sample data, and we find high correlations and low errors between the model specification and the observed flux. We emphasize that once the model is trained, the Van Allen Probes data are no longer needed at model run time; only the POES fluxes and the index are required to specify the outer electron belt using the model.

Architectural Concept of Disaggregation of Space Systems: Application to Weather Satellites

In the next decades, researchers and global decision makers will rely on new emerging technologies, architectural constructs, and ideas to reshape the space enterprise to meet many of their needs for global weather observation and information. One such new architectural concept is the disaggregation of space capabilities across multiple numbers of systems. Disaggregation has the potential to minimize cost per operational year and improve the system resiliency. Due to the cancellation of the National Polar-Orbiting Operational Environmental Satellite System program in 2010, both the U.S.’s National Oceanic and Atmospheric Administration and Department of Defense have started to investigate different acquisition approaches through the use of disaggregation to reduce the total program acquisition cost. This paper investigates the cost impacts of disaggregation across time for the weather follow-on systems. A merged system dynamics and trade space exploration technique is developed for the mission area of weather and climate sensing satellite systems. The merged model is simulated for both the systems to look at long-term trends and examine different levels of disaggregation across time. The impact of complexity on the cost metric is analyzed through the examination of different policies. Five different disaggregated implementations, each with a unique way of adding capability across future generations, are considered for the analysis of weather and climate sensing satellites. The model suggests a set of disaggregated approaches that, although not potentially cost effective, are able to reach higher efficiency and deliver additional capability to orbit in contrast to fully aggregated buses.

Intercalibration of Cross-Track Scanners in GPM Constellation

This paper discusses the intersatellite radiometric calibration for microwave sounders in support of NASA’s Global Precipitation Measurement (GPM) mission. This paper is an extension of previous GPM Intersatellite Calibration Working Group work, which assesses the robustness of the Central Florida Remote Sensing Laboratory “double difference” technique for sounders intercalibration. In this paper, we will analyze the intercalibration between the Advanced Technology Microwave Sounder on board the National Polar-orbiting Operational Environmental Satellite System Preparatory Project, the Microwave Humidity Sounder on board the MetOp-A and MetOp-B and NOAA-18 and NOAA-19, and the Sondeur Atmospherique du Profil d’Humidite Intertropicale par Radiometrie sounder onboard the Megha-Tropiques satellite. The sensitivity of the calibration to the geophysical parameters and incidence angles is investigated using two years data. Here, it is observed that a reliable intercalibration can be made only when the path lengths of the two sensors are similar, so when matching the scan angles for the two sensors, the sensitivity of the biases upon the water vapor profiles is significantly reduced.

Effects of diurnal adjustment on biases and trends derived from inter-sensor calibrated AMSU-A data

Measurements of brightness temperatures from Advanced Microwave Sounding Unit-A (AMSU-A) temperature sounding instruments onboard NOAA Polarorbiting Operational Environmental Satellites (POES) have been extensively used for studying atmospheric temperature trends over the past several decades. Intersensor biases, orbital drifts and diurnal variations of atmospheric and surface temperatures must be considered before using a merged long-term time series of AMSU-A measurements from NOAA-15, -18, -19 and MetOp-A.We study the impacts of the orbital drift and orbital differences of local equator crossing times (LECTs) on temperature trends derivable from AMSU-A using near-nadir observations from NOAA-15, NOAA-18, NOAA-19, and MetOp-A during 1998–2014 over the Amazon rainforest. The double difference method is firstly applied to estimation of inter-sensor biases between any two satellites during their overlapping time period. The inter-calibrated observations are then used to generate a monthly mean diurnal cycle of brightness temperature for each AMSU-A channel. A diurnal correction is finally applied each channel to obtain AMSU-A data valid at the same local time. Impacts of the inter-sensor bias correction and diurnal correction on the AMSU-A derived long-term atmospheric temperature trends are separately quantified and compared with those derived from original data. It is shown that the orbital drift and differences of LECTamong different POESs induce a large uncertainty in AMSU-A derived long-term warming/cooling trends. After applying an inter-sensor bias correction and a diurnal correction, the warming trends at different local times, which are approximately the same, are smaller by half than the trends derived without applying these corrections.

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.

RAM-SCB simulations of electron transport and plasma wave scattering during the October 2012 "double-dip" storm.

Mechanisms for electron injection, trapping, and loss in the near‐Earth space environment are investigated during the October 2012 “double‐dip” storm using our ring current‐atmosphere interactions model with self‐consistent magnetic field (RAM‐SCB). Pitch angle and energy scattering are included for the first time in RAM‐SCB using L and magnetic local time (MLT)‐dependent event‐specific chorus wave models inferred from NOAA Polar‐orbiting Operational Environmental Satellites (POES) and Van Allen Probes Electric and Magnetic Field Instrument Suite and Integrated Science observations. The dynamics of the source (approximately tens of keV) and seed (approximately hundreds of keV) populations of the radiation belts simulated with RAM‐SCB is compared with Van Allen Probes Magnetic Electron Ion Spectrometer observations in the morning sector and with measurements from NOAA 15 satellite in the predawn and afternoon MLT sectors. We find that although the low‐energy (E< 100 keV) electron fluxes are in good agreement with observations, increasing significantly by magnetospheric convection during both SYM‐H dips while decreasing during the intermediate recovery phase, the injection of high‐energy electrons is underestimated by this mechanism throughout the storm. Local acceleration by chorus waves intensifies the electron fluxes at E≥50 keV considerably, and RAM‐SCB simulations overestimate the observed trapped fluxes by more than an order of magnitude; the precipitating fluxes simulated with RAM‐SCB are weaker, and their temporal and spatial evolutions agree well with POES/Medium Energy Proton and Electron Detectors data.

Estimation of planetary boundary layer height using Suomi NPP-CrIS soundings

ABSTRACTThe study estimates planetary boundary layer height (PBLH) using temperature and humidity profiles from Cross-Track Infrared Sounder (CrIS) onboard Suomi National Polar-Orbiting Operational Environmental Satellite System Preparatory Project (SNPP). PBLH is estimated using six different methods and also using an integrated approach. PBLH estimated from SNNP-CrIS soundings by the integrated approach is compared with the PBLH values estimated using atmospheric profiles from radiosonde ascents and Constellation Observing System for Meteorology Ionosphere and Climate-radio occultation (COSMIC-RO) measurements. Analysis shows reasonable agreement of PBLH values from SNPP-CrIS soundings with those from radiosonde measurements and COSMIC-RO retrievals, thus revealing the capability of atmospheric profiles from SNNP-CrIS for the characterization of planetary boundary layer (PBL) with excellent spatial resolution and coverage. PBLH from SNNP-CrIS soundings are observed to be overestimated by around 336 m compared to the estimates from radiosonde ascends and is partly attributed to the difference in time of observations and coarse vertical resolution of the SNPP-CrIS-derived profiles. Compared to the estimates from SNPP-CrIS soundings, PBLH values from COSMIC-RO profiles are overestimated by around 596 m. Estimates from SNPP-CrIS soundings, through the integrated approach, are further used to examine the spatial and seasonal variations of PBLH over the Indian landmass. PBLH is observed highest in pre-monsoon and lowest in winter over most of the regions. Due to rainfall and associated changes in lower atmosphere and surface characteristics, PBLH is observed shallow during monsoon.

An Evaluation of HIRS Near-Surface Air Temperature Product in the Arctic with SHEBA Data

AbstractThe accuracy of cloud-screened 2-m air temperatures derived from the intersatellite-calibrated brightness temperatures based on the High Resolution Infrared Radiation Sounder (HIRS) measurements on board the National Oceanic and Atmospheric Administration (NOAA) Polar-Orbiting Operational Environmental Satellite (POES) series is evaluated by comparing HIRS air temperatures to 1-yr quality-controlled measurements collected during the Surface Heat Budget of the Arctic Ocean (SHEBA) project (October 1997–September 1998). The mean error between collocated HIRS and SHEBA 2-m air temperature is found to be on the order of 1°C, with a slight sensitivity to spatial and temporal radii for collocation. The HIRS temperatures capture well the temporal variability of SHEBA temperatures, with cross-correlation coefficients higher than 0.93, all significant at the 99.9% confidence level. More than 87% of SHEBA temperature variance can be explained by linear regression of collocated HIRS temperatures. The analysis found a strong dependency of mean temperature errors on cloud conditions observed during SHEBA, indicating that availability of an accurate cloud mask in the region is essential to further improve the quality of HIRS near-surface air temperature products. This evaluation establishes a baseline of accuracy of HIRS temperature retrievals, providing users with information on uncertainty sources and estimates. It is a first step toward development of a new long-term 2-m air temperature product in the Arctic that utilizes intersatellite-calibrated remote sensing data from the HIRS instrument.

A Framework for Studying Cost Growth on Complex Acquisition Programs

The government acquisition system is consistently plagued by cost growth and by attempts at acquisition reform. Despite these persistent challenges, the academic community lacks a methodology for studying complex acquisition programs both in-depth and longitudinally throughout their life cycles. In this paper, we present a framework for studying complex acquisition programs that provides researchers with a strategy for systematically studying cost growth mechanisms. The proposed framework provides a means to identify specific technical and organizational mechanisms for cost growth, to organize those mechanisms using design structure matrices, and to observe the evolution of those mechanisms throughout a program's life cycle. To illustrate the utility of our framework, we apply it to analyze a case study of the National Polar-orbiting Operational Environmental Satellite System NPOESS program. Ultimately, we demonstrate that the framework enables us to generate unique insights into the mechanisms that induced cost growth on NPOESS and that were unacknowledged by previous studies. Specifically, we observed that complexity was injected into the technical system well before the program's cost estimates began to increase and that it was the complexity of the NPOESS organization that hindered the program's ability to effectively estimate and to manage its costs.