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Correcting diurnal cycle aliasing in satellite microwave humidity sounder measurements
Author(s) -
Kottayil Ajil,
John Viju O.,
Buehler Stefan A.
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2012jd018545
Subject(s) - diurnal cycle , diurnal temperature variation , advanced microwave sounding unit , environmental science , depth sounding , atmospheric sciences , satellite , troposphere , microwave , amplitude , sampling (signal processing) , humidity , local time , climatology , meteorology , geology , geography , physics , oceanography , statistics , mathematics , quantum mechanics , astronomy , detector , optics
Microwave humidity measurements from polar orbiting satellites are affected by diurnal sampling biases which are caused by changes in the local observation time of the satellites. The long‐term data records available from these satellites thus have spurious trends, which must be corrected. Diurnal cycles of the microwave measurements have been constructed by combining data over the period 2001–2010 from five different satellite platforms (NOAA‐15, ‐16, ‐17, ‐18, and MetOpA). This climatological diurnal cycle has been used to deduce and correct the diurnal sampling bias in Advanced Microwave Sounding Unit‐B and microwave humidity sounder measurements. Diurnal amplitudes for channels which are sensitive to surface temperature variations show a sharp land‐sea contrast with the amplitudes exceeding 10 K for land regions but less than 1 K for oceanic regions. The humidity channels sensitive to the upper and middle troposphere exhibit a seasonal variation with large diurnal amplitudes over convective land regions (often above 3 K) in comparison to oceanic regions. The diurnal peak times of these channels over land occur in the early mornings. The diurnal sampling bias correction has a greater impact over land regions when compared to oceanic regions due to the large diurnal amplitudes over land. The diurnal cycle of humidity generated as a part of this study could be used to evaluate diurnal cycles in climate models.