Bias characterization of CrIS shortwave temperature sounding channels using fast NLTE model and GFS forecast field

Abstract

The strong nonlocal thermal equilibrium (NLTE) emission in the upper atmosphere impedes the usage of Cross-track Infrared Sounder (CrIS) temperature channels near 4.3 μm in the operational data assimilation. This study explores the bias characteristics of those temperature channels near 4.3 μm with and without a fast NLTE model implemented in the Community Radiative Transfer Model (CRTM). It is shown that the biases of those temperature channels can reach up to 12 K and are dramatically reduced to below 4 K during daytime by the fast NLTE model with small differences from the nighttime biases. However, the biases after applying the NLTE correction remain large for CrIS upper atmospheric temperature channels during both daytime and nighttime. A further investigation suggests that the remaining biases in those temperature channels mainly originate from the cold biases in the stratospheric temperature profiles of National Center for Environmental Prediction Global Forecast System (GFS) forecasts as input to CRTM. The cold biases reach the maximum of about 8 K near the tropics at about 1 hPa, decreasing toward higher latitudes and lower altitudes.where fg is the mathematical expectation operator. From the above equation, it is seen that the large differences between x o and x b are correlated to the large sum of μ o and μ b . Since the data assimilation YIN BIAS STATISTICS OF CRIS SW CHANNELS 1248 Key Points: • CrIS can provide the global infrared radiance in improving NWP forecast skills • The NLTE emission can introduce the large biases in CrIS shortwave temperature sounding channels • The NLTE effect on CrIS data bias is assessed by the fast NLTE model in CRTM Correspondence to: M. Yin, my11g@my.fsu.edu Citation: Yin, M. (2016), Bias characterization of CrIS shortwave temperature sounding channels using fast NLTE model and GFS forecast field,

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

“…To investigate this finding theoretically, we performed non-LTE CRTM calculations (e.g., Chen et al 2013;Yin 2016) to derive temperature kernel functions for all AIRS 15 and 4.3 mm channels at a range of different solar zenith angles x. Background temperature and constituent profiles were kept fixed in all cases.…”

The evaluation of FY4A's Geostationary Interferometric Infrared Sounder (GIIRS) long‐wave temperature sounding channels using the GRAPES global 4D‐Var

“…AIRS, IASI and CrIS). The departures of satellite observations from model simulations of these sounders that are on board polar‐orbit satellites often vary with the scan angle and geographic latitude (McNally et al ., ; Yin, ; Li and Zou, ). So, the widely adopted approaches for bias correction are scan angle BC and air‐mass BC (Susskind et al ., ; Eyre, ; Harris and Kelly, ; Auligne et al ., ).…”

“…() argued that the most appropriate way to study the bias characteristics of O – B for NWP systems is to use the short‐term forecast field as the background field. Also, considering that the forecast field is the next background field in the operational data assimilation system cycle (Yin, ), the GRAPES (Global/Regional Assimilation and Prediction Enhanced System)‐GFS (Global Forecast System) 6 hr forecast field is used as input to the radiative transfer model (RTTOV) for this study instead of the reanalysis fields. This will be conducive to the realization of GIIRS assimilation in the operational data assimilation system.…”

Improving the Understanding of CrIS Full Spectral Resolution Nonlocal Thermodynamic Equilibrium Radiances Using Spectral Correlation

“…All fast NLTE simulation studies found large discrepancies between B and O for large SZA in the high‐latitude region of the winter hemisphere. DeSouza‐Machado et al (2007) and Yin (2016) attributed this large discrepancy to the decreased accuracy of NWP profiles in the upper atmosphere for high latitudes. While the discrepancy is slightly reduced, it remains quite large after replacing GFS with the European Centre for Medium‐Range Weather Forecasts (ECMWF) Re‐Analysis (ERA) interim data (Yin, 2016).…”

“…Their evaluation shows a small bias (~ −0.5 K) and standard deviation of differences (STD) (less than 1.0 K) of background minus observation (BMO) for nadir observations with SZA less than 70° globally. Yin (2016) compared calculated nominal spectral resolution (NSR) CrIS/S‐NPP radiances with the CRTM using the Global Forecast System (GFS) forecast against CrIS observations over North and South Americas including the adjacent oceans. He showed that the BMO bias and STD from daytime after NLTE correction using the CRTM are comparable to those from nighttime without NLTE correction.…”