Abstract
The planetary boundary layer is the medium of energy, moisture, momentum and pollutant exchange between the surface and the atmosphere. In this paper, a method to derive the boundary layer mixing height (MH) was introduced and applied over the Heihe river basin. Atmospheric profiles from the MODerate Resolution Imaging Sepctroradiometer (MODIS) instrument onboard the NASA-Aqua satellite were used for the high spatial resolution of this method. A gap-filling method was used to replace missing MODIS data. In situ MH data were also calculated from HIWATER (Heihe Watershed Allied Telemetry Experimental Research) and WATER (Watershed Allied Telemetry Experimental Research) observational radiosonde sounding data from 2008 and 2012 using the Richardson number method combined with a subjective method. The MH occurs where there is an abrupt decrease in the MR (water vapor mixing ratio). The minimum vertical gradient of the MR is used to determine the MH. The method has an average RMSE of 370 m under clear skies and convective conditions. The seasonal variation in the MH at the Gaoya radiosonde station is also presented. The study demonstrates that remote sensing methodologies can successfully estimate the MH without the help of field measurements.
Highlights
The planetary boundary layer (PBL) or atmospheric boundary layer refers to the part of the atmosphere that is directly influenced by the Earth’s surface and responds to surface forces within a timescale of an hour or less [1,2]
The objective of the present study is to develop a method for estimating a high spatial-resolution mixing height (MH) and associated variables as input for a 1-km resolution surface energy balance system (SEBS) model for the
Several reasons may account for this daily variation: the MH is strongly related to net radiation, which has a large daily variation; there is a difference between the overpass times of the satellite on each day, and the diurnal variation of the MH can be as much as several kilometers; the presence of cloud cover, and the consequent use of gap-filling to estimate missing data may generate large errors in the moisture profile; under stable air conditions in particular, the automated MH
Summary
The planetary boundary layer (PBL) or atmospheric boundary layer refers to the part of the atmosphere that is directly influenced by the Earth’s surface and responds to surface forces within a timescale of an hour or less [1,2]. The mixing height (MH) is a key parameter for air pollution models, but is an important parameter in the surface energy balance system (SEBS) for the estimation of turbulent heat flux. In the application of pollution models, the MH determines the volume available for the dispersion of pollutants and is involved in many predictive and diagnostic methods and/or models to assess pollutant concentrations [3]. Evapotranspiration (ET) estimation models used for SEBS analysis require atmospheric data. These variables are estimated either from a large-scale meteorological model or from Obukhov similarity theory using data such as air pressure, temperature, humidity and wind speed at a reference height [4]
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