Comparison of spatial statistics of SAR-derived and in-situ soil moisture estimates

Hirsave, Praveen P.; Narayanan, Ram M.; Tracy, B.T.; Gwilliam, B.L.; Bolus, R.L.; Pangburn, Timothy; Mckim, H. L.

doi:10.1109/igarss.1996.516570

Cited by 1 publication

(1 citation statement)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, Jackson et al (1992) used a 21-cm passive microwave instrument to retrieve soil moisture over a semiarid area. Active systems, such as SAR (synthetic aperture radar), give better results in soil moisture retrieval, for example, Hirsave et al (1996). A combination of microwave and optical (visible and/or near-IR remote sensing can further improve the estimation of soil moisture and surface evaporation.…”

Section: Introductionmentioning

confidence: 99%

Urban Heat Island Modeling in Conjunction with Satellite-Derived Surface/Soil Parameters

Hafner¹,

Kidder²

1999

J. Appl. Meteor.

124

View full text Add to dashboard Cite

Although it has been studied for over 160 years, the urban heat island (UHI) effect is still not completely understood, yet it is increasingly important. The main purpose of this work is to improve UHI modeling by using AVHRR (Advanced Very High Resolution Radiometer) satellite data to retrieve the surface parameters (albedo, as well as soil thermal and moisture properties). In this study, a hydrostatic three-dimensional mesoscale model was used to perform the numerical modeling. The Carlson technique was applied to retrieve the thermal inertia and moisture availability using the thermal AVHRR channels 4 and 5. The net urban effect was determined as the difference between urban and nonurban simulations, in which urban parameters were replaced by rural parameters. Two winter days were each used for two numerical simulations: a control and an urban-to-rural replacement run. Moisture availability values on the less windy day showed generally a south to north gradient downwind of the city and urban values less than rural values (the urban dry island day). Moisture availability was higher on the windy day, with uniform values in the rural and urban areas (uniform soil moisture day). The only exceptions were variations in the rural hills north of the city and the low rural values under the polluted urban plume downwind of the city. While thermal inertia values showed no urban-rural differences on the uniform soil moisture day, they exhibited larger values over Atlanta than in surrounding rural area on the (less moist) dry island day. Two puzzling facts exist in the data: 1) lack of a north-south thermal inertia gradient on the dry soil day to correspond to its abovementioned moisture availability gradient and 2) rural thermal inertia values do not change between both days in spite of their large difference in soil moisture. The observed lack of corresponding urban change is expected, as its thermal inertia values depend more on urban building materials than on moisture of soil. In both cases both the 2-m and surface skin UHIs showed positive values at night and negative values (an urban cool island, UCI) during the day. The larger nighttime 2-m UHI was on the dry day (0.8Њ vs 0.6ЊC), while the larger daytime 2-m UCI was on the moist soil day (Ϫ0.3Њ vs Ϫ0.5ЊC). Note that the surface differences were almost always greater than the 2-m differences. These day-night differences imply a rural thermal inertia lower than its urban values on both days, which is in conflict with the observations on the wet uniform soil moisture day. On the uniform thermal inertia day (wet day), both the UHI and UCI amplitudes should be less than on the other day, but this is not the case. A possible explanation for both of these conflicts is the improper influence of the urban plume on this day on lowering the thermal inertia and moisture availability values used in the replacement urban simulation.

show abstract

Section: Introductionmentioning

confidence: 99%