H. K. Al Jassar

A model for the retrieval and monitoring of soil moisture over desert area of Kuwait

A simple statistical inversion model is developed for the retrieval of soil moisture, based on two frequencies. The model is applicable to desert semi‐arid areas such as Kuwait, where the surface is covered with scant vegetation and moderate roughness. In this study, Nimbus‐7 SMMR brightness temperature (T b) data at two bands (T b(H) of 6.6 GHz and T b(V) of 37 GHz) acquired during the six‐year period (1979–1985) are used for the retrieval and monitoring of soil moisture. The model parameters are fine‐tuned with field data. The accuracy of estimation of soil moisture is of the order of 3%. The soil moisture varies from 1% (in dry summer) to 13% (during the rainy period), with an average of 4%.

THE TEMPERATURE EFFECT IN SECONDARY COSMIC RAYS (MUONS) OBSERVED AT THE GROUND: ANALYSIS OF THE GLOBAL MUON DETECTOR NETWORK DATA

The analysis of cosmic ray intensity variation seen by muon detectors at Earths surface can help us to understand astrophysical, solar, interplanetary and geomagnetic phenomena. However, before comparing cosmic ray intensity variations with extraterrestrial phenomena, it is necessary to take into account atmospheric effects such as the temperature effect. In this work, we analyzed this effect on the Global Muon Detector Network (GMDN), which is composed of four ground-based detectors, two in the northern hemisphere and two in the southern hemisphere. In general, we found a higher temperature influence on detectors located in the northern hemisphere. Besides that, we noticed that the seasonal temperature variation observed at the ground and at the altitude of maximum muon production are in antiphase for all GMDN locations (low-latitude regions). In this way, contrary to what is expected in high-latitude regions, the ground muon intensity decrease occurring during summertime would be related to both parts of the temperature effect (the negative and the positive). We analyzed several methods to describe the temperature effect on cosmic ray intensity. We found that the mass weighted method is the one that best reproduces the seasonal cosmic ray variation observed by the GMDN detectors and allows the highest correlation with long-term variation of the cosmic ray intensity seen by neutron monitors.

An assessment of brightness temperature data quality of MSMR of IRS‐P4 satellite

Frequency dependence of brightness temperature (T B) in the range 6–21 GHz is studied as a function of surface roughness, vegetation cover and soil moisture using theoretical models. Frequency dependence of T B is plotted from Multi‐channel Scanning Microwave Radiometer (MSMR) T B data of Indian Remote Sensing Satellite (P‐series) IRS‐P4 for different target types such as ocean, desert, forest, agricultural and snow regions. MSMR responds to the variations of the target parameters; however, it is noticed that the T B data at 18 GHz deviate from the theoretically predicted trend. The effect of atmosphere (water vapour) is taken into account in the theoretical trend. However, the frequency dependence of T B plots from Scanning Multi‐channel Microwave Radiometer (SMMR) of Nimbus‐7 closely resemble the theoretical trend. This indicates that the relative calibration of 18 GHz T B of IRS‐P4 has some problem and needs to be looked into. Approximate offset values for each land type are computed and presented here. A general comparison of T B of MSMR and SMMR indicates that T B of MSMR is higher by 4 K, which needs to be further investigated.

Time series analysis of SAR interferometry derived DEM of Kuwait desert to reduce the affects of atmosphere

Twenty five ASAR scenes are analyzed to find the suitable pairs for generating DEM of Kuwait desert area. About 40 pairs are suitable for generating DEMs. A unique combination of seven DEM are possible with a single master image whose perpendicular baseline component varies between 233 to 393m. GAMMA inerferometric package coupled with ERDAS image processing package are used in the analysis. The seven DEMs are compared with the 90 m DEM derived from SRTM. It has been found that the RMS error varies from 1.9 m to 15.3 m. The highest RMS error refers to day-difference of 525 days with average coherence value of 0.71 (lowest of all). Therefore, correlation will be the cause of higher errors. However, 35 days day-difference pair gave RMS error of 5.5 m with highest coherence value (0.93) which is supposed to produce the lowest RMS error. For the study of spatial distribution of errors, Interferometric DEMs are subtracted from DEM of SRTM. From this analysis, it is observed that the atmospheric affects are aligned and varies systematically. It can give an error in elevation as high as 15 m. Therefore, one should be very careful in using SAR interfoermetry technology for DEM generation even for desert regions.