Cross-track Infrared Sounder Research Articles

The Impact of Low Latency Satellite Sounder Observations on Local Severe Storm Forecasts in Regional NWP.

The forecasts of local severe storms (LSS) are highly dependent on how well the pre-convection environment is characterized in the numerical weather prediction (NWP) model analysis. The usefulness of the forecasts is highly dependent on how frequently the forecast is updated. Therefore, the data latency is critical for assimilation into regional NWP models for it to be able to assimilate more data within the data cut-off window. These low latency data can be obtained through direct broadcast sites and direct receiving systems. Observing system experiments (OSE) were performed to study the impact of data latency on the LSS forecasts. The experiments assimilated all existing observations including conventional data (from the global telecommunication system, GTS) and satellite sounder radiance data (AMSU-A (The Advanced Microwave Sounding Unit-A), ATMS (Advanced Technology Microwave Sounder), CrIS (Cross-track Infrared Sounder), and IASI (Infrared Atmospheric Sounding Interferometer)). They were carried out in a nested domain with a horizontal resolution of 9 km and 3 km in the weather research and forecasting (WRF) model. The forecast quality scores of the LSS precipitation forecasts were calculated and compared with different data cut-off widows to evaluate the impact of data latency. The results showed that low latency can lead to an improved and positive impact on precipitation and other forecasts, which indicates the potential application of LEO direct broadcast (DB) data in a high-resolution regional NWP for LSS forecasts.

Atmospheric ammonia variability and link with particulate matter formation: a case study over the Paris area

Abstract. The Paris megacity experiences frequent particulate matter (i.e.PM2.5, particulate matter with a diameter less than 2.5 µm) pollution episodes in spring (March–April). At this time of the year, large numbers of the particles consist of ammonium sulfate and nitrate which are formed from ammonia (NH3) released during fertilizer spreading practices and transported from the surrounding areas to Paris. There is still limited knowledge of the emission sources around Paris, their magnitude, and their seasonality. Using space-borne NH3 observation records of 10 years (2008–2017) and 5 years (2013–2017) provided by the Infrared Atmospheric Sounding Interferometer (IASI) and the Cross-Track Infrared Sounder (CrIS) instrument, regional patterns of NH3 variabilities (seasonal and interannual) are derived. Observations reveal identical high seasonal variability with three major NH3 hotspots found from March to August. The high interannual variability is discussed with respect to atmospheric total precipitation and temperature. A detailed analysis of the seasonal cycle is performed using both IASI and CrIS instrument data, together with outputs from the CHIMERE atmospheric model. For 2014 and 2015, the CHIMERE model shows coefficients of determination of 0.58 and 0.18 when compared to IASI and CrIS, respectively. With respect to spatial variability, the CHIMERE monthly NH3 concentrations in spring show a slight underrepresentation over Belgium and the United Kingdom and an overrepresentation in agricultural areas in the French Brittany–Pays de la Loire and Plateau du Jura region, as well as in northern Switzerland. In addition, PM2.5 concentrations derived from the CHIMERE model have been evaluated against surface measurements from the Airparif network over Paris, with which agreement was found (r2 = 0.56) with however an underestimation during spring pollution events. Using HYSPLIT cluster analysis of back trajectories, we show that NH3 total columns measured in spring over Paris are enhanced when air masses originate from the north-east (e.g. the Netherlands and Belgium), highlighting the importance of long-range transport in the NH3 budget over Paris. Variability in NH3 in the north-east region is likely to impact NH3 concentrations in the Parisian region since the cross-correlation function is above 0.3 (at lag = 0 and 1 d). Finally, we quantify the key meteorological parameters driving the specific conditions important for the formation of PM2.5 from NH3 in the Île-de-France region in spring. Data-driven results based on surface PM2.5 measurements from the Airparif network and IASI NH3 measurements show that a combination of the factors such as a low boundary layer of ∼500 m, a relatively low temperature of 5 ∘C, a high relative humidity of 70 %, and wind from the north-east contributes to a positive PM2.5 and NH3 correlation.

A potential application of height-dependent cloud emission and scattering indices for identifying CrIS clear channels above clouds

Satellite data assimilation of hyperspectral Cross-track Infrared Sounder (CrIS) clear channels in regions with but not affected by low-level clouds requires a set of height-dependent cloud emission and scattering indices (CESIs) that are sensitive to cloud top pressures. In this study, three CESIs are generated by pairing CrIS longwave and shortwave channels at three altitudes around 212 (CESI-5), 452 (CESI-9) and 1085 hPa (CESI-19). The training dataset for CESIs is the European Centre for Medium-Range Weather Forecasting analysis. CESI-5 is strongly (weakly) affected by those ice clouds with cloud-top pressures (CTPs) above (below) ∼300 hPa; CESI-9 is strongly (weakly) affected by those ice clouds with CTPs above (below) ∼600 hPa; and CESI-19 is highly correlated with the ice cloud optical depth (ICOD) obtained from the Atmospheric Infrared Sounder (AIRS) retrieval product. CESIs have latitudinal and scan-dependent biases that need removal. Verified with AIRS ICOD data, CESI-19 is greater than 5 K (6.5 K) if an ice cloud is present. This 5-K threshold gives a probability of correct typing of 85.3% (86.5%), a false alarm rate of 9.5% (5.1%) and a leakage rate of 4.5% (5.0%) during the daytime (nighttime). CESI-5 (CESI-9) is greater than −3 K (−1 K) if an ice cloud is present above 200 hPa (between 200 and 300 hPa). The case of Typhoon Maria (2018) demonstrates the potential of using height-dependent CESIs to identify above-cloud CrIS clear channels.

An Algorithm for Detecting Ice Cloud at Different Altitudes by Combining Dual CrIS Full Spectrum Resolution CO2 Channels

Using infrared sensors to detect ice clouds in different atmospheric layers is still a challenge. The different scattering and absorption properties of longwave and shortwave infrared channels can be utilized to fulfill this purpose. In this study, the release of Suomi-NPP Cross-track Infrared Sounder (CrIS) full spectrum resolution is used to select and pair channels from longwave (~ 15 μm) and shortwave (~4.3 μm) CO2 absorption bands under stricter conditions, so as to better detect ice clouds. Besides, the differences of the weighting function peaks and cloud insensitive level altitudes of the paired channels are both within 50 hPa so that the variances due to atmospheric conditions can be minimized. The training data of clear sky are determined by Visible Infrared Imaging Radiometer Suite (VIIRS) cloud mask product and used to find the linear relationship between the paired longwave and shortwave CO2 absorption channels. From the linear relationship, the so-called cloud emission and scattering index (CESI) is derived to detect ice clouds. CESI clearly captures the center and the ice cloud features of the Super Typhoon Hato located above 415 hPa. Moreover, the CESI distributions agree with cloud top pressure from the VIIRS in both daytime and nighttime in different atmospheric layers.

Assessment of the Hyperspectral Infrared Atmospheric Sounder (HIRAS)

The hyperspectral infrared atmospheric sounder (HIRAS), the first Chinese hyperspectral infrared instrument, was launched in 2017 on board the fourth polar orbiter of the Feng Yun 3 series, FY-3D. The instrument is a Fourier transform spectrometer with 2275 channels covering three spectral bands (650–1136, 1210–1750, and 2155–2550 cm−1) with 0.625 cm−1 spectral resolution. The first data quality assessment of HIRAS observations at full and normal spectral resolutions is presented. Comparisons with short-range forecasts from the Met Office numerical weather prediction (NWP) global system have revealed biases (standard deviation) generally less than 2.6 K (2 K) in the spectral regions mostly unaffected by trace gases where the confidence in the NWP model is largest. Of particular concern, HIRAS detector 3 seems to suffer from sunlight contamination of its calibration towards the end of the descending node. This, together with an obstruction of the detector field of view by an element of the platform, results in accentuated bias and noise in the observations from this detector. At normal spectral resolution, a background departure double difference analysis has been conducted between HIRAS and the NOAA-20 crosstrack infrared sounder (CrIS). The results show that HIRAS and CrIS are in good agreement with a mean difference across the three bands of −0.05 K (±0.26 K at 1σ) and 75.2% of the channels within CrIS radiometric uncertainty, noting though that HIRAS is noisier than CrIS with, on average, a standard deviation 0.34 K larger.

Improved Lunar Intrusion Detection Algorithm for the CrIS Sensor Data Record

As one of the calibration reference targets used to calibrate the cross-track infrared sounder (CrIS) earth scene (ES) measurements, the stable deep space (DS) reference spectrum in the 30-scan DS calibration moving window is very important for the accuracy of the calibrated ES radiances. The DS view changes when the lunar radiation intrudes into the observation field of view (FOV). In the original CrIS lunar intrusion (LI) detection algorithm implemented in the operational ground processing system, the contaminated DS spectra were not effectively removed from the DS moving window due to large threshold values and the assumption that the first DS spectrum in the moving window was not contaminated. As a result, inaccurate, degraded, or invalid ES radiances were produced in the operational CrIS sensor data record (SDR) during LI events. In this article, an improved LI detection algorithm is developed and implemented into the operational system. First, the new algorithm efficiently finds a contamination-free DS spectrum in the DS 30-scan calibration moving window to use as the reference spectrum. Second, based on the phase characteristics of the complex raw DS spectra during LI events, the LI band-dependent thresholds were derived to effectively reject the contaminated DS spectra and to make the valid DS window size consistent among the three CrIS bands. The new LI algorithm implemented in the operational system shows a successful detection and removal of all the lunar-contaminated DS spectra in the DS moving window, resulting in an improved calibration of ES radiances during LI events.

NH<sub>3</sub> emissions from large point sources derived from CrIS and IASI satellite observations

Abstract. Ammonia (NH3) is an essential reactive nitrogen species in the biosphere and through its use in agriculture in the form of fertilizer (important for sustaining humankind). The current emission levels, however, are up to 4 times higher than in the previous century and continue to grow with uncertain consequences to human health and the environment. While NH3 at its current levels is a hazard to environmental and human health, the atmospheric budget is still highly uncertain, which is a product of an overall lack of measurements. The capability to measure NH3 with satellites has opened up new ways to study the atmospheric NH3 budget. In this study, we present the first estimates of NH3 emissions, lifetimes and plume widths from large (>∼5 kt yr−1) agricultural and industrial point sources from Cross-track Infrared Sounder (CrIS) satellite observations across the globe with a consistent methodology. The same methodology is also applied to the Infrared Atmospheric Sounding Interferometer (IASI) (A and B) satellite observations, and we show that the satellites typically provide comparable results that are within the uncertainty of the estimates. The computed NH3 lifetime for large point sources is on average 2.35±1.16 h. For the 249 sources with emission levels detectable by the CrIS satellite, there are currently 55 locations missing (or underestimated by more than an order of magnitude) from the current Hemispheric Transport Atmospheric Pollution version 2 (HTAPv2) emission inventory and only 72 locations with emissions within a factor of 2 compared to the inventories. The CrIS emission estimates give a total of 5622 kt yr−1, for the sources analyzed in this study, which is around a factor of ∼2.5 higher than the emissions reported in HTAPv2. Furthermore, the study shows that it is possible to accurately detect short- and long-term changes in emissions, demonstrating the possibility of using satellite-observed NH3 to constrain emission inventories.

Stratospheric Gravity Wave Products from Satellite Infrared Nadir Radiances in the Planning, Execution, and Validation of Aircraft Measurements during DEEPWAVE

AbstractGravity wave perturbations in 15-μm nadir radiances from the Atmospheric Infrared Sounder (AIRS) and Cross-Track Infrared Sounder (CrIS) informed scientific flight planning for the Deep Propagating Gravity Wave Experiment (DEEPWAVE). AIRS observations from 2003 to 2011 identified the South Island of New Zealand during June–July as a “natural laboratory” for observing deep-propagating gravity wave dynamics. Near-real-time AIRS and CrIS gravity wave products monitored wave activity in and around New Zealand continuously within 10 regions of scientific interest, providing nowcast guidance and validation for flight planners. A novel technique used these gravity wave products to validate upstream forecasts of nonorographic gravity waves with 1–2-day lead times, providing time to plan flight intercepts as tropospheric westerlies brought forecast source regions into range. Postanalysis verifies the choice of 15μm radiances for nowcasting, since 4.3-μm gravity wave products yielded spurious diurnal cycles, provided no altitude sensitivity, and proved relatively insensitive to deep gravity wave activity over the South Island. Comparisons of DEEPWAVE flight tracks with AIRS and CrIS gravity wave maps highlight successful repeated vectoring of the aircraft into regions of deep orographic and nonorographic gravity wave activity, and how background winds control the amplitude of waves in radiance perturbation maps. We discuss how gravity wave information in AIRS and CrIS radiances might be directly assimilated into future operational forecasting systems.

Direct retrieval of isoprene from satellite-based infrared measurements

Isoprene is the atmosphere’s most important non-methane organic compound, with key impacts on atmospheric oxidation, ozone, and organic aerosols. In-situ isoprene measurements are sparse, and satellite-based constraints have employed an indirect approach using its oxidation product formaldehyde, which is affected by non-isoprene sources plus uncertainty and spatial smearing in the isoprene-formaldehyde relationship. Direct global isoprene measurements are therefore needed to better understand its sources, sinks, and atmospheric impacts. Here we show that the isoprene spectral signatures are detectable from space using the satellite-borne Cross-track Infrared Sounder (CrIS), develop a full-physics retrieval methodology for quantifying isoprene abundances from these spectral features, and apply the algorithm to CrIS measurements over Amazonia. The results are consistent with model output and in-situ data, and establish the feasibility of direct global space-based isoprene measurements. Finally, we demonstrate the potential for combining space-based measurements of isoprene and formaldehyde to constrain atmospheric oxidation over isoprene source regions.

Imager and sounder data fusion to generate sounder retrieval products at an improved spatial and temporal resolution

The Visible Infrared Imaging Radiometer Suite (VIIRS) imaging instrument on the polar-orbiting Suomi-National Polar-orbiting Partnership and National Oceanic and Atmospheric Administration-20 satellite platforms has infrared window bands but no carbon dioxide and water vapor absorption bands; the latter are essential for accurately deriving atmospheric variables (such as temperature and moisture profiles, cloud properties). An approach for fusing a high spatial resolution imager (e.g., VIIRS) and a high spectral resolution sounder [e.g., Cross-track Infrared Sounder (CrIS)] offers the opportunity to construct new spectral band radiances (radiance fusion) as well as sounder retrieval products (product fusion) at high spatial resolution. Furthermore, temperature and humidity profiles can also be provided at a high temporal resolution when geostationary imager [Advanced Baseline Imager (ABI)] data are used in combination with polar orbiting sounder (CrIS) data in a fusion approach. Promising results from VIIRS/CrIS and ABI/CrIS fusion are presented.

Assessment of the CubeSat Infrared Atmospheric Sounder impact on global numerical weather prediction using observational system simulation experiments

The CubeSat Infrared Atmospheric Sounder (CIRAS) is a proposed small satellite IR sounder developed in response to the challenges of high cost and possible data gaps for currently operational hyperspectral IR sounders, such as Atmospheric Infrared Sounder, Infrared Atmospheric Sounding Interferometer, and Crosstrack Infrared Sounder. A key objective of CIRAS is to demonstrate the technologies required for a low cost-to-orbit, operational IR sounder. CIRAS was designed by National Aeronautics and Space Administration’s Jet Propulsion Laboratory, with 625 channels measuring upwelling IR radiation of the Earth in the mid-wavelength IR spectrum region. Through observational system simulation experiments, the impact of assimilating CIRAS on global numerical weather prediction was assessed. CIRAS was simulated by applying the Community Radiative Transfer Model to profiles extracted from the Goddard Earth Observing System Model, Version 5 nature run for an afternoon polar orbiting sensor, and then assimilated by the National Centers for Environmental Prediction Global Data Assimilation System. Assimilating CIRAS improved global analysis and forecasts, when added to the currently operational observing configuration and to a data gap scenario.

Inter-Comparing SNPP and NOAA-20 CrIS Toward Measurement Consistency and Climate Data Records

The cross-track infrared sounder (CrIS) is a Fourier transform spectrometer that provides hyperspectral soundings of the atmosphere over three wavelength ranges onboard on both Suomi National Polar-orbiting Partnership (SNPP) and NOAA-20 satellites. Quantifying the radiometric difference and creating a calibration link between SNPP and NOAA-20 CrIS are crucial for creating CrIS long-term climate data records and establishing the space-based calibration standard. This study explores the inter-comparison strategy to identify the radiometric differences between SNPP and NOAA-20 CrIS along the finest spectral scale, including 1) direct comparison; and 2) the two double difference methods using infrared atmospheric sounding interferometer and radiative transfer calculations as transfer targets. Each method has its own advantages and disadvantages. The preliminary results based on the above methods suggest good agreement generally between SNPP and NOAA-20 CrIS. Some consistent findings are disclosed by the above three methods, including 1) around the CO2 absorption band at 650–750 cm−1 range, a consistent warm bias is found on the level of 0.1 K; 2) at the water vapor absorption band, the two CrIS instruments are well consistent to each other and their BT differences are close to zero lines albeit with spectral variation; 3) the largest BT difference of more than –0.6 K is found at the spectral line transition region (around 2380 cm−1). The root causes still need further investigation.

Using Sounder Data to Improve Cirrus Cloud Height Estimation from Satellite Imagers

AbstractModern polar-orbiting meteorological satellites provide both imaging and sounding observations simultaneously. Most imagers, however, do not have H2O and CO2 absorption bands and therefore struggle to accurately estimate the height of optically thin cirrus clouds. Sounders provide these needed observations, but at a spatial resolution that is too coarse to resolve many important cloud structures. This paper presents a technique to merge sounder and imager observations with the goal of maintaining the details offered by the imager’s high spatial resolution and the accuracy offered by the sounder’s spectral information. The technique involves deriving cloud temperatures from the sounder observations, interpolating the sounder temperatures to the imager pixels, and using the sounder temperatures as an additional constraint in the imager cloud height optimal estimation approach. This technique is demonstrated using collocated VIIRS and Cross-track Infrared Sounder (CrIS) observations with the impact of the sounder observations validated using coincident CALIPSO/CALIOP cloud heights These comparisons show significant improvement in the cloud heights for optically thin cirrus. The technique should be generally applicable to other imager/sounder pairs.

Improving the Calibration of Suomi NPP VIIRS Thermal Emissive Bands During Blackbody Warm-Up/Cool-Down

The Suomi National Polar-orbiting Partnership Program Visible Infrared Imaging Radiometer Suite (VIIRS) thermal emissive bands (TEB) have been performing well during nominal operations since launch. However, small but persistent calibration anomalies are observed in all TEBs during the quarterly blackbody (BB) warm-up/cool-down (WUCD) events. As a result, the time series of daytime sea surface temperature (SST) (derived from bands M15–M16) show warm spikes on the order of 0.25 K. This paper suggests that VIIRS TEB WUCD biases are band dependent, with daily-averaged biases about −0.04 and 0.05 K for I4 and I5, and −0.05, −0.05, 0.11, 0.09, and 0.05 K for M12–M16, respectively. Two correction methods—Ltrace and WUCD-C—have been implemented and evaluated using colocated observations from the Cross-track Infrared Sounder (CrIS), radiative transfer simulations, and SST retrievals. Also an error in the National Oceanic and Atmospheric Administration operational processing was identified and fixed. Both correction methods effectively minimize WUCD-induced SST anomalies. The Ltrace method works well for I5, M12, and M14–M16, with residual biases about 0.01 K. The WUCD-C method, on the other hand, performs well to correct WUCD biases in all TEBs, with residual biases also about 0.01 K. However, it introduces warm biases relative to CrIS at cold scene temperatures, which requires further study. Applying nonequal BB thermistor weights improves calibration at BB temperature set points, but its impact on daily-averaged WUCD biases is small. The proposed methodologies may also be applied to the VIIRS onboard the follow-on Joint Polar Satellite System satellites.

An Alternative Bias Correction Scheme for CrIS Data Assimilation in a Regional Model

Bias correction (BC) is a crucial step for satellite radiance data assimilation (DA). In this study, the traditional airmass BC scheme in the National Centers for Environmental Prediction (NCEP) Gridpoint Statistical Interpolation (GSI) is investigated for Cross-track Infrared Sounder (CrIS) DA. The ability of the airmass predictors to model CrIS biases is diagnosed. Correlations between CrIS observation-minus-background ( O − B) samples and the two lapse rate–related airmass predictors employed by GSI are found to be very weak, indicating that the bias correction contributed by the airmass BC scheme is small. A modified BC scheme, which directly calculates the moving average of O − B departures from data of the previous 2 weeks with respect to scan position and latitudinal band, is proposed and tested. The impact of the modified BC scheme on CrIS radiance DA is compared with the variational airmass BC scheme. Results from 1-month analysis/forecast experiments show that the modified BC scheme removes nearly all scan-dependent and latitude-dependent biases, while residual biases are still found in some channels when the airmass BC scheme is applied. Smaller predicted root-mean-square errors of temperature and specific humidity and higher equivalent threat scores are obtained by the DA experiment using the modified BC scheme. If O − B samples are replaced by observation-minus-analysis ( O − A) samples for bias estimates in the modified BC scheme, the forecast impacts are reduced but remain positive. A convective precipitation case that occurred on 21 August 2016 is investigated. Using the modified BC scheme, the atmospheric temperature structure and the geopotential height structures near trough/ridge areas are better resolved, resulting in better precipitation forecasts.

AIRS Deconvolution and the Translation of AIRS-to-CrIS Radiances With Applications for the IR Climate Record

Spectra of the earth’s thermal emission as measured by the Atmospheric InfraRed Sounder (AIRS), Cross-track Infrared Sounder (CrIS), and Infrared Atmospheric Sounding Interferometer (IASI) hyperspectral sounders are becoming a significant part of the long-term climate record. These instruments have broadly similar spatial sampling, spectral resolution, and band spans. However, the spectral response functions differ in detail, leading to significant differences in observed spectra. To address this, we translate channel radiances from one sounder to another, including simulation of the response functions of the translation target. We make regular use of such translations from AIRS to CrIS and IASI to CrIS and have implemented and tested IASI-to-AIRS and CrIS-to-AIRS translations as well. Our translation from AIRS to CrIS has some novel features. AIRS is a grating spectrometer with a distinct response function for each channel, whereas CrIS is a Michaelson interferometer with a sinc response function after calibration and corrections. We use our detailed knowledge of the AIRS spectral response functions to deconvolve AIRS channel radiances to a resolution-enhanced intermediate representation. This is reconvolved to CrIS or other instrument specifications. The resulting translation is shown to be more accurate than interpolation or regression.

Satellite-derived emissions of carbon monoxide, ammonia, and nitrogen dioxide from the 2016 Horse River wildfire in the Fort McMurray area

Abstract. In May 2016, the Horse River wildfire led to the evacuation of ∼ 88 000 people from Fort McMurray and surrounding areas and consumed ∼ 590 000 ha of land in Northern Alberta and Saskatchewan. Within the plume, satellite instruments measured elevated values of CO, NH3, and NO2. CO was measured by two Infrared Atmospheric Sounding Interferometers (IASI-A and IASI-B), NH3 by IASI-A, IASI-B, and the Cross-track Infrared Sounder (CrIS), and NO2 by the Ozone Monitoring Instrument (OMI). Daily emission rates were calculated from the satellite measurements using fire hotspot information from the Moderate Resolution Imaging Spectroradiometer (MODIS) and wind information from the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis, combined with assumptions on lifetimes and the altitude range of the plume. Sensitivity tests were performed and it was found that uncertainties of emission estimates are more sensitive to the plume shape for CO and to the lifetime for NH3 and NOx. The satellite-derived emission rates were ∼ 50–300 kt d−1 for CO, ∼ 1–7 kt d−1 for NH3, and ∼ 0.5–2 kt d−1 for NOx (expressed as NO) during the most active fire periods. The daily satellite-derived emission estimates were found to correlate fairly well (R∼0.4–0.7) with daily output from the ECMWF Global Fire Assimilation System (GFAS) and the Environment and Climate Change Canada (ECCC) FireWork models, with agreement within a factor of 2 for most comparisons. Emission ratios of NH3∕CO, NOx∕CO, and NOx∕NH3 were calculated and compared against enhancement ratios of surface concentrations measured at permanent surface air monitoring stations and by the Alberta Environment and Parks Mobile Air Monitoring Laboratory (MAML). For NH3∕CO, the satellite emission ratios of ∼ 0.02 are within a factor of 2 of the model emission ratios and surface enhancement ratios. For NOx∕CO satellite-measured emission ratios of ∼0.01 are lower than the modelled emission ratios of 0.033 for GFAS and 0.014 for FireWork, but are larger than the surface enhancement ratios of ∼0.003, which may have been affected by the short lifetime of NOx. Total emissions from the Horse River fire for May 2016 were calculated and compared against total annual anthropogenic emissions for the province of Alberta in 2016 from the ECCC Air Pollutant Emissions Inventory (APEI). Satellite-measured emissions of CO are ∼1500 kt for the Horse River fire and exceed the total annual Alberta anthropogenic CO emissions of 992.6 kt for 2016. The satellite-measured emissions during the Horse River fire of ∼30 kt of NH3 and ∼7 kt of NOx (expressed as NO) are approximately 20 % and 1 % of the magnitude of total annual Alberta anthropogenic emissions, respectively.

Cross-Track Infrared Sounder Spectral Gap Filling Toward Improving Intercalibration Uncertainties

The cross-track infrared sounder (CrIS) is a hyper-spectral infrared sounder with 2211 (full-spectral resolution) channels over three wavelength ranges. Due to its excellent calibration and high spectral resolution, CrlS radiances are also used as an infrared reference to check calibration accuracy of other narrow- or broadband instruments. However, there are spectral gaps between the CrlS bands, which impact the accuracy of intercomparison between CrlS and other instruments. To fill up the spectral gaps, this paper develops a new method to predict the CrlS gap channels. A training data set was first built based on the spectra selected from different seasons to represent different atmospheric and surface conditions. The principal component regression method is then developed to derive the prediction coefficients between the CrlS measured and the gap channel spectra. The prediction accuracies are around 0.005 K ± 0.18 mK, 0.06 K ± 0.45 mK, and 0.05 K ± 0.71 mK for the long-, middle-, and short-wave gap channels, respectively. It should note that the predicted channels are intended to be only used in the intercomparison purposes instead of providing exact information of these gap channels. When comparing the CrlS gap radiances with atmospheric infrared sounder and infrared atmospheric sounding interferometer, consistent results are observed between CrIS and other sounders. The further intercomparison results with visible infrared imaging radiometer suite and advanced baseline imager suggest that the predicted gap radiances are good enough for the intercalibration purposes and this method can be confidently applied in global space-based intercalibration system community.

Toward the Operational Weather Forecasting Application of Atmospheric Stability Products Derived From NUCAPS CrIS/ATMS Soundings

Atmospheric soundings from radiosondes are critical for the weather forecasting, particularly for the diagnostic of atmospheric stability conditions that can lead to thunderstorm development. However, radiosonde observations (RAOBs) are temporally and spatially limited throughout the globe, promoting the use of satellite measurements. This paper assesses the applicability to the operational short-term weather forecasting of atmospheric stability indices and parameters (SIPs) derived from thermodynamic profiles retrieved from the National Oceanic and Atmospheric Administration Unique Combined Atmospheric Processing System (NUCAPS) using the Suomi National Polar-orbiting Partnership (SNPP) Cross-track Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) radiances. For this purpose, we validated NUCAPS SIPs against SIPs derived from conventional and dedicated/reference RAOBs collocated with NUCAPS retrievals within a maximum radius of 50 km and ±1-h time difference, over midlatitudes (60°N-30°N) and tropics (30°N-30°S). Stability parameters evaluated include total precipitable water (TPW), lifted index, K-index, total-totals index, and Galvez-Davison index. NUCAPS TPW exhibited the highest level of statistical agreement with RAOBs, with the remaining NUCAPS SIPs exhibiting favorable results (linear correlations ranging between 0.65 and 0.85). Case studies over the Texas/Oklahoma region and the Northern Coast of Brazil demonstrate NUCAPS capability of generating reliable fields of atmospheric stability, as well as capturing synoptic-scale convective signatures, not feasible with RAOBs. Considering also the benefit of SNPP NUCAPS hyperspectral-infrared (IR) and microwave soundings available for both regions during critical early afternoon periods, our analysis supports the use of NUCAPS CrIS/ATMS SIPs as complementary nowcasting tools for the analysis of preconvective environments.

Intercomparison Between VIIRS and CrIS by Taking Into Account the CrIS Subpixel Cloudiness and Viewing Geometry

AbstractThe Cross‐track Infrared Sounder (CrIS) onboard the Suomi National Polar‐orbiting Partnership (SNPP) has high radiometric accuracy, which can be used to intercompare and understand the radiometric performance of the thermal emissive bands of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the same platform. Previous studies usually selected uniform scenes to avoid potential uncertainties due to geolocation errors. This study focuses on all scenes (including nonuniform scenes), as well as CrIS subpixel cloudiness, local zenith angle and surface type, and their impacts on VIIRS/CrIS intercomparisons. A geolocation error correction scheme is applied to mitigate the geolocation mismatch between CrIS and VIIRS. Intercomparison results of three days from 19 to 21 September 2016, a quarterly warm up/cool down calibration period, show overall good agreement in terms of radiance biases (less than 0.2 K in terms of brightness temperature) between VIIRS and CrIS, for scene temperatures between 220 and 300 K; however, larger biases are evident outside of this range. The three factors—CrIS subpixel cloudiness, local zenith angle, and surface type—show weak impacts on VIIRS radiance biases. Both clear‐sky and overcast conditions have slightly different radiance biases from other partially cloudy conditions because of more contributions from colder or warmer scenes. The time series show the impact of warm up/cool down and the effectiveness of the correction algorithm for reprocessing VIIRS M15 and M16 data sets. The methods and tools can be applied to monitor and validate other infrared imager/sounder duos onboard the same platform.