Updating Soil Information in the Noah Land Surface Model for Simulations in Texas.

In regional simulation of weather, climate changes and air quality assessments, realistic representation of soil parameterization is critical because moisture and heat exchange at the soil surface strongly influence the boundary layer conditions between land and atmosphere. The default soil parameters applied in the Community NOAH Land Surface Model (NOAH LSM) were developed based on a nation-wide soil data set, but with limited number of samples more than a decade ago. The objective of this study was to test the influence of revising the default table of the soil parameters in the NOAH LSM based on mean estimates from soil data collected in areas typical in Texas. In 12 major classes of soil texture, data of 6,749 soil samples was used that included 693 top-layer samples with geographic coordinates. To determine texture classes at unsampled locations, 1534 sample points with texture records and spatial coordinates were selected and interpolated over a gridded area of Texas. Our findings indicated that 118 out of 190 (62.1%) of parameter values in the default soil parameter table were significantly different from means of soil data in Texas and adjacent regions within its major land resource areas (MLRAs). Evaluation of estimated soil water contents in field capacity and wilting point conditions conducted by using hydraulic functions developed based on the proposed parameters BB, MAXSMC and SATPSI demonstrated good agreement between estimated soil water in 95 % of the cases. The estimated soil water contents were within the ranges of standard deviations around the means in 11 of the 12 texture classes, except for sandy clay. Spatial variability of soil parameters was demonstrated across MLRAs. Evaluating the impact of revised default parameters is planned on the NOAH model outcomes and on assessments of air quality using WRF coupled with NOAH LSM.