Long-term Ground-based Broadband Microwave Scatterometer Observations of an Alpine Meadow over the Tibetan Plateau

A ground-based microwave scatterometer was installed on an alpine meadow over the Tibetan Plateau to study the soil moisture and -temperature dynamics of the top soil layer and air-to-soil interface during the period August 2017 - July 2019. The radar return (amplitude and phase) of the ground surface was measured over 1 - 10 GHz in the four linear polarization combinations (vv, hh, hv, vh) at hourly or half-hourly intervals . This dataset contains both the (raw) radar return values (amplitude and phase) and the backscattering coefficients derived from it (vv and hh only). Included are results from the time-series measurements over the period August 2017 - August 2018 and results of experiments (during three days in summer) where the ground backscatter was measured under various incidence- and azimuth angles. Also measurement results from calibration standards are included. Finally, In-situ measurement results of the volumetric soil moisture and soil temperature (at various depths) and precipitation for the complete period are added to this dataset

Long-term Ground-based Broadband Microwave Scatterometer Observations of an Alpine Meadow over the Tibetan Plateau

A ground-based microwave scatterometer was installed on an alpine meadow over the Tibetan Plateau to study the soil moisture and-temperature dynamics of the top soil layer and air-to-soil interface during the period August 2017 - July 2019. The radar return (amplitude and phase) of the ground surface was measured over 1 - 10 GHz in the four linear polarization combinations (vv, hh, hv, vh) at hourly or half-hourly intervals . This dataset contains both the (raw) radar return values (amplitude and phase) and the backscattering coefficients (sigma0) derived from it for four bands: 1.5 - 1.75 GHz (L-band), 2.5 - 3.0 GHz (s-band), 4.5 - 5.0 GHz (C-band), 9.0 - 10.0 GHz (X-band). Included are results from the time-series measurements over the period August 2017 - August 2018 and results of experiments (during three days in summer) where the ground backscatter was measured under various incidence- and azimuth angles. Also measurement results from calibration standards are included. Matlab scripts for retrieving sigma0 for other frequency bands are also included. Finally, in-situ measurement of volumetric soil moisture and soil temperature (at various depths), air temperature, precipitation, and short- and long wave Irradiance for the complete period are added to this dataset

Matlab source code for retrieving backscatter coefficients

A ground-based microwave scatterometer was installed on an alpine meadow over the Tibetan Plateau to study the soil moisture and-temperature dynamics of the top soil layer and air-to-soil interface during the period August 2017 - July 2019. The radar return (amplitude and phase) of the ground surface was measured over 1 - 10 GHz in the four linear polarization combinations (vv, hh, hv, vh) at hourly or half-hourly intervals . This dataset contains Matlab scripts that can be used to import the scatterometer measurement data and process it into backscattering coefficients

Long-term Ground-based Broadband Microwave Scatterometer Observations of an Alpine Meadow over the Tibetan Plateau

A ground-based microwave scatterometer was installed on an alpine meadow over the Tibetan Plateau to study the soil moisture and-temperature dynamics of the top soil layer and air-to-soil interface during the period August 2017 - July 2019. The radar return (amplitude and phase) of the ground surface was measured over 1 - 10 GHz in the four linear polarization combinations (vv, hh, hv, vh) at hourly or half-hourly intervals . This dataset contains both the (raw) radar return values (amplitude and phase) and the backscattering coefficients (sigma0) derived from it for four bands: 1.5 - 1.75 GHz (L-band), 2.5 - 3.0 GHz (s-band), 4.5 - 5.0 GHz (C-band), 9.0 - 10.0 GHz (X-band). Included are results from the time-series measurements over the period August 2017 - August 2018 and results of experiments (during three days in summer) where the ground backscatter was measured under various incidence- and azimuth angles. Also measurement results from calibration standards are included. Finally, in-situ measurement of volumetric soil moisture and soil temperature (at various depths), air temperature, precipitation, and short- and long wave Irradiance for the complete period are added to this dataset

Matlab source code for retrieving backscatter coefficients

A ground-based microwave scatterometer was installed on an alpine meadow over the Tibetan Plateau to study the soil moisture and-temperature dynamics of the top soil layer and air-to-soil interface during the period August 2017 - July 2019. The radar return (amplitude and phase) of the ground surface was measured over 1 - 10 GHz in the four linear polarization combinations (vv, hh, hv, vh) at hourly or half-hourly intervals . This dataset contains Matlab scripts that can be used to import the scatterometer measurement data and process it into backscattering coefficients

Microwave scattering (1-10 GHz) from a vertically heterogeneous grass canopy

This study concerns the effects of considering vertically heterogeneous canopy structure when modeling microwave scattering from grassland with the Tor Vergata (TVG) model, which uses the matrix doubling method (MDM). The TVG model was extended with the M-volume approach to accommodate height-dependent variation in structure for every scatterer type. Used approach was to reproduce 1 – 10 GHz backscatter for all linear polarization combinations from an alpine meadow measured by a ground-based scatterometer with both the default (1-volume) and the M-volume approach with 3 volumes. Measured in-situ vegetation parameters were used to constrain the model. We found that both models were able to reproduce the angle-dependent backscattering for C- and X-band, measured on two afternoons, and the 31-day average measured radar return power for L-, S-, C-, and X-band within, or close to, the measurement uncertainty. Our analysis proved inconclusive on whether the 1- or 3-volume approach worked better for the considered grassland, but did show that the 3-volume approach allows for more flexibility in reproducing the actual angle-dependent backscattering for multiple frequencies, a flexibility that may prove necessary when more scattering angles are considered. Furthermore, predictions of the bistatic scattering coefficient at higher frequencies (C- and X-band) were significantly different between both models. For X-band with hh polarization differences up to 3 dB were found for the specular direction. We conclude that considering vertical heterogeneity of vegetation canopy structure with MDM leads to significantly different results than with the vertically homogeneous canopy approximations typically used

Active and passive microwave signatures of diurnal soil freeze-thaw transitions on the Tibetan Plateau

Active and passive microwave characteristics of diurnal soil freeze-thaw transitions and their relationships are crucial for developing retrieval algorithms of the soil liquid water content (θliq) and freeze/thaw state, which, however, have been less explored. This study investigates these microwave characteristics and relationships via analysis of ground-based measurements of brightness temperature (TB) and backscattering coefficients (σ⁰) in combination with simulations performed with the Tor Vergata discrete radiative transfer model. Both an L-band (1.4 GHz) radiometer ELBARA-III and a wide-band (1-10 GHz) scatterometer are installed in a seasonally frozen Tibetan meadow ecosystem to measure diurnal variations of TB and copolarized σ⁰ at both hh (σhh⁰) and vv (σ vv⁰) polarizations. Analysis of measurements collected between December 2017 and March 2018 shows that 1) diurnal cycles are observed in both TB and σ ⁰ due to the change in surface θliq caused by diurnal soil freeze-thaw transitions; 2) a negatively linear relationship is found between e and σ⁰ regardless of frequency, polarization combinations, and observation angles; 3) slopes (β ) of linearly fit equations between eH and σhh⁰ decrease with increasing observation angles of ELBARA-III, while the ones between eV and σvv⁰ increase with increasing observation angles; and 4) correlations between e and σ⁰ increase with decreasing microwave frequency of σ⁰ measurements and ELBARA-III observation angles, and magnitudes of diurnal σ⁰ cycles also increase with decreasing microwave frequency. Moreover, the calibrated Tor Vergata model shows capability to reproduce both diurnal e and σ⁰ variations as well as to quantify their relationships at different frequencies and observation angles

Monitoring water and energy cycles at climate scale in the Third Pole Environment (CLIMATE-TPE)

A better understanding of the water and energy cycles at climate scale in the Third Pole Environment is essential for assessing and understanding the causes of changes in the cryosphere and hydrosphere in relation to changes of plateau atmosphere in the Asian monsoon system and for predicting the possible changes in water resources in South and East Asia. This paper reports the following results: (1) A platform of in situ observation stations is briefly described for quantifying the interactions in hydrosphere-pedosphere-atmosphere-cryosphere-biosphere over the Tibetan Plateau. (2) A multiyear in situ L-Band microwave radiometry of land surface processes is used to develop a new microwave radiative transfer modeling system. This new system improves the modeling of brightness temperature in both horizontal and vertical polarization. (3) A multiyear (2001–2018) monthly terrestrial actual evapotranspiration and its spatial distribution on the Tibetan Plateau is generated using the surface energy balance system (SEBS) forced by a combination of meteorological and satellite data. (4) A comparison of four large scale soil moisture products to in situ measurements is presented. (5) The trajectory of water vapor transport in the canyon area of Southeast Tibet in different seasons is analyzed, and (6) the vertical water vapor exchange between the upper troposphere and the lower stratosphere in different seasons is presented