A Novel Near-Land Radiometer Wet Path-Delay Retrieval Algorithm: Application to the Jason-2/OSTM Advanced Microwave Radiometer

Abstract. This paper is to investigate the uncertainties of microwave radiometer (MWR) retrievals in snow conditions and also explore the discrepancies of MWR retrievals in zenith and off-zenith observations. The MWR retrievals were averaged in a ±15 min period centered at sounding times of 00:00 and 12:00 UTC and compared with radiosonde observations (RAOBs). In general, the MWR retrievals have a better correlation with RAOB profiles in off-zenith observations than in zenith observations, and the biases (MWR observations minus RAOBs) and root mean square errors (RMSEs) between MWR and RAOB are also clearly reduced in off-zenith observations. The biases of temperature, relative humidity, and vapor density decrease from 4.6 K, 9 %, and 1.43 g m−3 in zenith observations to −0.6 K, −2 %, and 0.10 g m−3 in off-zenith observations, respectively. The discrepancies between MWR retrievals and RAOB profiles by altitude present the same situation. Cases studies show that the impact of snow on accuracies of MWR retrievals is more serious in heavy snowfall than in light snowfall, but off-zenith observation can mitigate the impact of snowfall. The MWR measurements become less accurate in snowfall mainly due to the retrieval algorithm, which does not consider the effect of snow, and the accumulated snow on the top of the radome increases the signal noise of MWR measurements. As the snowfall drops away by gravity on the sides of the radome, the off-zenith observations are more representative of the atmospheric conditions for RAOBs.

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Sentinel-3 Microwave Radiometers: Instrument Description, Calibration and Geophysical Products Performances

Remote Sensing ◽

10.3390/rs12162590 ◽

2020 ◽

Vol 12 (16) ◽

pp. 2590 ◽

Cited By ~ 1

Author(s):

Marie-Laure Frery ◽

Mathilde Siméon ◽

Christophe Goldstein ◽

Pierre Féménias ◽

Franck Borde ◽

...

Keyword(s):

Microwave Radiometer ◽

Instrument Design ◽

Sea Surface ◽

Double Difference ◽

Path Delay ◽

Vicarious Calibration ◽

Difference Methods ◽

Two Parameters ◽

Microwave Radiometers ◽

Single Instrument

Copernicus Sentinel-3 Surface Topography Mission embarks a two-channel microwave radiometer combined with the altimeter in order to correct the altimeter range for the excess path delay resulting from the presence of water vapour in the troposphere. The in-flight calibration of a single instrument is the critical point to achieve the expected performances. In the context of a constellation, the inter-calibration is even more important. After a presentation of the instrument design, we present the diagnoses used for the calibration of Sentinel-3A, using vicarious calibration over specific areas and double difference methods. The inter-calibration of Sentinel-3B with Sentinel-3A is performed during the tandem phase, using the residual differences of co-located measurements. Finally performances are assessed at crossover points with two parameters, first the wet troposphere correction by comparison with Jason-3; secondly on the Sea Surface Height by difference of variance. Analysis results have shown that Sentinel-3A is well calibrated, consistent with other instruments, and that Sentinel-3B is calibrated within 0.4 K with Sentinel-3A as a reference. Performances and stability fulfill the requirements for both missions.

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Tropospheric wet path-delay measurements

IRE Transactions on Antennas and Propagation ◽

10.1109/tap.1982.1142808 ◽

1982 ◽

Vol 30 (3) ◽

pp. 502-505 ◽

Cited By ~ 14

Author(s):

G. Elgered

Keyword(s):

Path Delay ◽

Wet Path Delay

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The application of FengYun-3 Microwave Radiation Imager soil moisture product in drought monitoring

10.5194/egusphere-egu2020-13688 ◽

2020 ◽

Author(s):

Ruijing Sun ◽

Yeping Zhang ◽

Shengli Wu

Keyword(s):

Soil Moisture ◽

Microwave Radiation ◽

Snow Water Equivalent ◽

Surface Soil ◽

Microwave Radiometer ◽

Empirical Relationship ◽

Drought Monitoring ◽

Retrieval Algorithm ◽

Severe Drought ◽

Drought Event

<p>FY-3(Feng Yun 3) satellites series are the China&#8217;s second-generation polar-orbiting meteorological satellites. FY-3B is the second satellite of FY3 series which was launched on November 5, 2010. One of the eleven instruments on board the FY-3B satellite is the Microwave Radiation Imager (MWRI) which is a highly sensitive microwave radiometer. It is China&#8217;s first space-borne microwave radiometer. It has 5 different frequencies from 10.65GHz to 89GHz with dual polarization. The MWRI instrument provides measurements of terrestrial, oceanic, and atmospheric parameters, including precipitation rate, sea ice concentration, snow water equivalent, soil moisture, atmospheric cloud water, and water vapor. Soil moisture, as a key parameter in the drought monitoring, becomes especially concerned. The FY-3B/MWRI soil moisture product provides global observations of land surface soil moisture. The current soil moisture retrieval algorithm of FY-3B/MWRI uses the brightness temperature with both v and h polarizations of 10.65GHz to eliminate the effects of surface roughness and vegetation simultaneously. For the bare surface soil estimation part, the algorithm is based on a parameterized surface emission model (the Qp model) which uses a physically based soil moisture inversion technique for application with passive microwave measurements. For the vegetation correction part, the algorithm uses the empirical relationship between the NDVI and the vegetation water content to estimate the vegetation optical depth. The spatial resolution of FY-3B/MWRI soil moisture product is 0.25&#176;&#215;0.25&#176;. In recent years, drought occurs frequently worldwide. As the only microwave sensor which operationally provides global soil moisture products currently in china, the FY-3B/MWRI soil moisture product plays an important part in drought monitoring during the meteorological service. In the summer of 2014, Henan Province which is located in the middle area of China suffered severe drought. The soil moisture of this area remained a very low level all along until significant precipitation finally came in last September. In the year of 2018, there was a severe drought occurred in Afghan, we used a long-time data series to analyze this drought event. The result showed that the FY-3B/MWRI soil moisture can objectively reflect the spatial distribution and development process of drought. This paper will give an introduction of the applications of FY-3B/MWRI soil moisture product during these drought event.</p>

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