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Ground-based microwave radiometers are getting great attention in recent years due to their capability to profile the temperature and humidity at high temporal and vertical resolution in the lower troposphere. The process of retrieving these parameters from the measurements of radiometric brightness temperature (T B ) includes the inversion algorithm, which uses the back ground information from a forward model. In the present study, an algorithm development and evaluation of this forward model for a ground-based microwave radiometer, being developed by Society for Applied Microwave Electronics Engineering and Research (SAMEER) of India, is presented. Initially, the analysis of absorption coefficient and weighting function at different frequencies was made to select the channels. Further the range of variation of T B for these selected channels for the year 2011, over the two stations Mumbai and Delhi is discussed. Finally the comparison between forward-model simulated T B s and radiometer measured T B s at Mahabaleshwar (73.66 ∘E and 17.93∘N) is done to evaluate the model. There is good agreement between model simulations and radiometer observations, which suggests that these forward model simulations can be used as background for inversion models for retrieving the temperature and humidity profiles.

The agreement of two ground-based microwave radiometers during the Temperature, hUmidity, and Cloud (TUC) profiling campaign has been evaluated in terms of measured brightness temperature. To account effectively the instruments' specifications, we discuss and estimate an equivalent monochromatic frequency, which significantly reduces the bias introduced by ideal monochromatic modelling. The effect of this equivalent monochromatic frequency can reach 0.4 K and thus we recommend its use in further study involving TUC radiometers. This analysis showed agreement within expectations for three of the four selected pairs of channels, although results are strictly valid in a limited range. As a consequence, the derived products are expected to be of the same quality. However, the inconsistency found in the remaining pair is expected to propagate in the retrieved humidity profiles.

Multi-frequency microwave radiometers (3-09, 5-4, 9-6, 36GHz) designed by the Changchun Institute of Geography have been used to measure dual-polarized brightness temperature of different crop canopies in the People's Republic of China. A numerical modelling of radiative transfer of multi-layer random media is developed. All parameters calculated by the empirical formulations arc chosen in a consistent way. Numerical results arc compared with the experimental measurements. The functional dependence of brightness tempera-lure on frequency, polarization, observation angle and crop parameters such as moisture content, crop height, etc. arc numerically discussed.

In order to correct the altimeter range for tropospheric humidity, a microwave radiometer is added to altimetry missions [Envisat/microwave radiometer, Jason/Jason Microwave Radiometer, and TOPEX-Poseidon/TOPEX Microwave Radiometer (TMR)]. Over open ocean, the combination altimeter/radiometer is satisfactory. This is not the case in coastal zones, where the signal coming from the surrounding land surfaces contaminates the radiometer measurement and makes the humidity-retrieval method unsuitable. In this paper, a radiometer simulator is built, using data from a field experiment (in situ measurements and collocated TMR measurements) and analyses from a mesoscale-forecast model. This simulator is used to perform sensitivity tests and to evaluate the current methods to retrieve the wet tropospheric correction in transition areas. The purpose of this paper is to analyze and compare the performances of these methods. After examining simple correction methods (extension of the open-sea wet tropospheric correction and use of the meteorological model value), we evaluated the feasibility and performances of two methods, which propose to take into account the land-surface effect in the brightness-temperature estimation. The latter was found to give significantly better results.

The optimal pair of frequencies for dual-frequency radiometer presuming the presence of clouds and accounting on the possible accuracy of the instrument are investigated. The water vapor and liquid water contents retrieved from microwave measurements with dual-frequency radiometer were averaged over various types of clouds. To reduce the influence of strong cloud conditions the third frequency band is proposed. Optimal frequency set is estimated in the case of zenith-looking observation.

Passive microwave radiometers have found varied geophysical applications, particularly the remote sensing from satellites of atmospheric temperature and humidity profiles, clouds, soil moisture, snow and ice type and coverage, and other parameters.

The SSM/T-1 B3 and SSM/T-2 B4 units were successfully launched on August 29th, 1994. The SSM/T-2 instrument is a five channel, microwave total-power radiometer. It has three channels near the 183.31 GHz water vapor resonance line and two window channels (91 GHz and 150 GHz). The SSM/T-1 is a cross-track step scanning seven-channel Dicke microwave radiometer instrument. It operates in the oxygen absorption region at center frequencies of 50.5, 53.2, 54.35, 54.9, 58.4, 58.9, and 59.4 GHz. At a nominal orbit at an altitude of 833 km, brightness temperatures from the SSM/T-1 and SSM/T-2 instruments are used in the AFGWC's (Air Force Global Weather Center) weather prediction models. The SSM/T-2 ground processing software provides profiles of relative humidity, and absolute humidity, and water vapor mass at six mandatory pressure levels. The SSM/T-1 ground processing software estimates air temperature profiles at fifteen pressure levels and the tropopause. The SSM/T-1 f33 and SS. >