Modeling and Synthesis of 3-D Water Vapor Fields for EM Wave Propagation Applications

Stochastic model of water vapor (SMOV), a methodology to generate realistic 3-D spatially correlated water vapor fields, is presented, which is devised by investigating remote sensing observations acquired by the MODIS sensor (Aqua satellite). Synthetic water vapor fields are 200 km × 200 km, with 1 km × 1 km horizontal spatial resolution, while the water vapor content v extends up to 20 km with a vertical sampling of 100 m. The field synthesis relies on the stochastic approach proposed by Bell and requires as input the average integrated water vapor content provided with coarse spatial and temporal resolution by numerical weather prediction (NWP) products. The vertical profile of v is modeled as a simple exponential function decreasing with height, as observed from typical radiosonde observations and NWP data. Tests on the model's accuracy show that both first-order (complementary cumulative distribution function) and second-order (spatial distribution) statistics of the integrated water vapor content are closely reproduced in several European sites. Results corroborate the use of SMOV as part of a comprehensive simulator of atmospheric impairments, which aims at taking into account all the constituents affecting the propagation of millimeter waves in different scenarios, including applications involving very low elevation links such as unmanned aerial vehicles and low Earth orbit satellites.