Vertical Moisture Distribution Research Articles

Зависимость отражательных свойств агропочв в сверхширокой полосе частот от типа, степени шероховатости поверхности и профилей влажности агропочв

In this article, the impact of volumetric moisture from 0% to 40% (vertical moisture profiles), dry bulk density from 0.4 to 1.8 g/cm3, clay content from 0.15 to 0.55 g/g (agrosoil type), standard deviations heights of surface roughness from 0 to 4 cm of soil on the variations of reflection coefficient in the ultra-wide frequency band from 100-400 MHz to 1.26-2.4 GHz were investigated. The reflection coefficient was calculated for a smooth and rough soil surface. Mironov's two-relaxation dielectric model was used (input parameters: dry bulk density, clay content, volumetric moisture, frequency of electromagnetic wave) to calculating the reflection coefficient. It is shown that the reflection coefficient is an ambiguous function of the clay content and the dry bulk density; the error in retrieving high values of soil moisture can be 5 times higher than for dry soils. In relation to the clay content and the dry bulk density, the soil roughness is the dominant parameter, which uncertainty, significantly effects on the error of soil moisture retrieving. For the considered various vertical profiles of soil moisture, it is shown that the effective thickness of topsoil, which forms the reflection coefficient, does not exceed 2 cm at a sensing frequency above 1 GHz. When the volumetric moisture content of soil surface is more than 28%, the reflection coefficient in the frequency range from 433 MHz to 1.26 GHz does not depend on the vertical distribution of moisture in soil. The conducted studies establish quantitative limitations on the accuracy of soil moisture retrieval for a given error in the initial parameters of the model: the clay content, the dry bulk density, soil surface roughness, which should be taken into account when developing algorithms for remote sensing of agrosoil moisture.

Tropospheric Moisture Sounding Using Microwave Imaging Channels: Application to GCOM-W1/AMSR2

Traditionally, space-based microwave imagers have been used exclusively for providing total atmospheric water vapor along with hydrometeor and surface parameters, using a combination of window channels. These channels operate away from the strong water vapor absorption lines used for atmospheric moisture sounding. Nevertheless, they are sensitive to the vertical distribution of moisture in the atmosphere. This is due to the fact that the water vapor absorption continuum varies monotonically, and the wing effect of the strong absorption lines has a nonconstant effect, across the microwave spectrum. Therefore, the transmittances of window channels are different, allowing a varying level of penetration into the atmospheric column. To demonstrate the capability of imagers to operate as sounders, we introduce penetration depth, which defines the vertical sensitivity of window channels to moisture. In addition, we evaluate the degree to which data from spaceborne microwave imagers, specifically the Global Change Observation Mission-Water 1 (GCOM-W1) Advanced Microwave Scanning Radiometer-2 (AMSR2) sensor, can be used to perform sounding of tropospheric moisture. The capability is assessed using numerical weather prediction (NWP) analysis as the reference. In simulations using a regression approach, the performance of AMSR2 moisture sounding matches that of Suomi-NPP ATMS up to 700 hPa, with standard deviations of 10%–20%. AMSR2 outperforms other pure moisture sounders (Microwave Humidity Sounder and Sondeur Atmospherique du Profil d’Humidite Intertropicale par Radiometrie) up to 500 hPa, before degrading rapidly. The performances using real observations and a physical algorithm are consistent with those found in simulations. These results highlight new applications for microwave imagers like GCOM-W1 AMSR2, including in Nowcasting and NWP, which are heavily reliant on lower tropospheric moisture information.

A seamless weather–climate multi‐model intercomparison on the representation of a high impact weather event in the western Mediterranean: HyMeX IOP12

High Impact Weather (HIW), particularly Heavy Precipitation Events (HPE), are common phenomena affecting the western Mediterranean (WMED) especially in the autumn period. Understanding and evaluating the capability to adequately represent such events in model simulations is one of the main goals of the Hydrological cycle in the Mediterranean Experiment (HyMeX) and the main motivation of this investigation.In order to gain a better knowledge of the model representation of HPE and related processes we perform a seamless multi‐model intercomparison at the event scale. Limited‐area model runs (grid spacing from 2 to 20 km) at weather and climate time‐scales are considered, four with parametrized and five with explicit convection. The performance of the nine models is compared by analysing precipitation, as well as convection‐relevant parameters. An Intensive Observation Period (IOP12) from the HyMeX‐SOP1 (Special Observation Period) is used to illustrate the results. During IOP12, HPE affected the northwestern Mediterranean region, from Spain to Italy, as a consequence of Mesoscale Convective Systems (MCSs) which initiated and intensified in the area of investigation.Results show that: (i) the timing of the maximum precipitation seems to be linked to the representation of large‐scale conditions rather than differences among models; (ii) Convection Permitting Models (CPMs) exhibit differences among each other, but better represent the short‐intense convective events. All four convection‐parametrized models produce a large number of weak and long‐lasting events. Regional Climate Models (RCMs) capture the occurrence of the event but produce notably lower precipitation amounts and hourly intensities than CPMs and Numerical Weather Prediction (NWP) models with parametrized convection; (iii) these differences do not seem to come from mean moisture or Convective Available Potential Energy (CAPE) which are in the same range for all models, but rather from differences in the variability and vertical distribution of moisture and the triggering of deep convection.

Practical Predictability of the 20 May 2013 Tornadic Thunderstorm Event in Oklahoma: Sensitivity to Synoptic Timing and Topographical Influence

Abstract The practical predictability of severe convective thunderstorms during the 20 May 2013 severe weather event that produced the catastrophic enhanced Fujita scale 5 (EF-5) tornado in Moore, Oklahoma, was explored using ensembles of convective-permitting model simulations. The sensitivity of initiation and the subsequent organization and intensity of the thunderstorms to small yet realistic uncertainties in boundary layer and topographical influence within a few hours preceding the thunderstorm event was examined. It was found that small shifts in either simulation time or terrain configuration led to considerable differences in the atmospheric conditions within the boundary layer. Small shifts in simulation time led to changes in low-level moisture and instability, primarily through the vertical distribution of moisture within the boundary layer due to vertical mixing during the diurnal cycle as well as advection by low-level jets, thereby influencing convection initiation. Small shifts in terrain led to changes in the wind field, low-level vertical wind shear, and storm-relative environmental helicity, altering locally enhanced convergence that may trigger convection. After initiation, an upscale growth of errors resulting from deep moist convection led to large forecast uncertainties in the timing, intensity, structure, and organization of the developing mesoscale convective system and its embedded supercells.

The effect of texture and irrigation on the soil moisture vertical-temporal variability in an urban artificial landscape: a case study of Olympic Forest Park in Beijing

Soil moisture variability in natural landscapes has been widely studied; however, less attention has been paid to its variability in the urban landscapes with respect to the possible influence of texture stratification and irrigation management. Therefore, a case study was carried out in the Beijing Olympic Forest Park to continuously monitor the soil in three typical profiles from 26 April to 11 November 2010. The texture stratification significantly affected the vertical distribution of moisture in the non-irrigated profile where moisture was mostly below field capacity. In the profile where irrigation was sufficient to maintain moisture above field capacity, gravity flow led to increased moisture with depth and thus eliminated the influence of texture. In the non-irrigated sites, the upper layer (above 80 cm) exhibited long-term moisture persistence with the time scale approximating the average rainfall interval. However, a coarse-textured layer weakened the influence of rainfall, and a fine-textured layer weakened the influence of evapotranspiration, both of which resulted in random noise-like moisture series in the deeper layers. At the irrigated site, frequent irrigation neutralized the influence of evapotranspiration in the upper layer (above 60 cm) and overshadowed the influence of rainfall in the deeper layer. As a result, the moisture level in the upper layer also behaved as a random noise-like series; whereas due to deep transpiration, the moisture of the deep layer had a persistence time-scale longer than a month, consistent with characteristic time-scales found for deep transpiration.

Assessment of Regional Global Climate Model Water Vapor Bias and Trends Using Precipitable Water Vapor (PWV) Observations from a Network of Global Positioning Satellite (GPS) Receivers in the U.S. Great Plains and Midwest

Abstract Precipitable water vapor (PWV) observations from the National Center of Atmospheric Research (NCAR) SuomiNet networks of ground-based global positioning system (GPS) receivers and the National Oceanic and Atmospheric Administration (NOAA) Profiler Network (NPN) are used in the regional assessment of global climate models. Study regions in the U.S. Great Plains and Midwest highlight the differences among global climate model output from the Fourth Assessment Report (AR4) Special Report on Emissions Scenarios (SRES) A2 scenario in their seasonal representation of column water vapor and the vertical distribution of moisture. In particular, the Community Climate System model, version 3 (CCSM3) is shown to exhibit a dry bias of over 30% in the summertime water vapor column, while the Goddard Institute for Space Studies Model E20 (GISS E20) agrees well with PWV observations. A detailed assessment of vertical profiles of temperature, relative humidity, and specific humidity confirm that only GISS E20 was able to represent the summertime specific humidity profile in the atmospheric boundary layer (<3%) and thus the correct total column water vapor. All models show good agreement in the winter season for the region. Regional trends using station-elevation-corrected GPS PWV data from two complimentary networks are found to be consistent with null trends predicted in the AR4 A2 scenario model output for the period 2000–09. The time to detect (TTD) a 0.05 mm yr−1 PWV trend, as predicted in the A2 scenario for the period 2000–2100, is shown to be 25–30 yr with 95% confidence in the Oklahoma–Kansas region.

Advances in thermal infrared remote sensing for land surface modeling

Over 10 years ago, John Norman and co-authors proposed a thermal-based land surface modeling strategy that treated the energy exchange and kinetic temperatures of the soil and vegetated components in a unique “Two-Source Model” (TSM) approach. The TSM formulation addresses key factors affecting the convective and radiative exchange within the soil–canopy–atmosphere system, focusing on the relationship between radiometric and aerodynamic temperature. John Norman's contribution came at a time when thermal-based techniques applied to standard “One-Source Model” (OSM) for large scale land surface flux and evapotranspiration (ET) estimation were generally considered unreliable and not viable for operational remote sensing applications. Others have subsequently modified OSM schemes to accommodate the radiometric–aerodynamic temperature relationship for partial canopy cover conditions, approaching accuracies achieved with the TSM. In this study, Norman's TSM and two current OSM schemes are evaluated over a range in canopy cover and moisture conditions simulated by the Cupid model—a complex soil–vegetation–atmosphere transfer (SVAT) scheme developed by Norman that simulates the complete radiation, convection/turbulence and hydrologic processes occurring at the soil/canopy interface. The use of SVAT simulations permitted the evaluation of TSM and OSM approaches over a greater range of hydrometeorological and vegetation cover conditions than typically available from field observations. The utility of the TSM versus OSM approaches in handling extremes in moisture/vegetation cover conditions simulated by the SVAT model Cupid is presented. Generally the TSM approach outperformed the OSM schemes for the extreme conditions. Moreover, the ability of the TSM to partition ET into evaporation and transpiration components provides additional hydrologic information about the moisture status of the soil and canopy system, and about the vertical distribution of moisture in the soil profile (surface layer vs. root zone). Examples for actual landscapes are presented in the application of the TSM as incorporated within in the Atmosphere Land EXchange Inverse/Disaggregation ALEXI (ALEXI/DisALEXI) modeling system, designed for operational applications at local to continental scales using multi-scale thermal imagery. This strategy for utilizing radiometric surface temperature in land surface modeling has converted many skeptics and more importantly rejuvenated many in the research and operational remote sensing community to reconsider the utility of thermal infrared remote sensing for monitoring land surface fluxes from local to regional scales.

Vertical Distribution of Moisture in a Growing Sweet Corn Canopy During MicroWEX-4

Circular 1492, a 9-page illustrated report by Joaquin Casanova, Jasmeet Judge, and Mi-young Jang, describes the methods and measurements of the canopy moisture distribution in sweet corn during a growing season. Published by the UF Department of Agricultural and Biological Engineering, August 2006. CIR1492/AE395: Vertical Distribution of Moisture in a Growing Sweet Corn Canopy During MicroWEX-4 (ufl.edu)

Contrail Frequency over the United States from Surface Observations

Contrails have the potential for affecting climate because they impact the radiation budget and the vertical distribution of moisture. Estimating the effect requires additional knowledge about the temporal and spatial variations of contrails. The mean hourly, monthly, and annual frequencies of daytime contrail occurrence are estimated using 2 yr of observations from surface observers at military installations scattered over the continental United States. During both years, persistent contrails are most prevalent in the winter and early spring and are seen least often during the summer. They co-occur with cirrus clouds 85% of the time. The annual mean persistent contrail frequencies in unobscured skies dropped from 0.152 during 1993–94 to 0.124 in 1998–99 despite a rise in air traffic. Mean hourly contrail frequencies reflect the pattern of commercial air traffic, with a rapid increase from sunrise to midmorning followed by a very gradual decrease during the remaining daylight hours. Although highly correlated with air traffic fuel use, contrail occurrence is governed by meteorological conditions. It is negatively and positively correlated with the monthly mean 300-hPa temperature and 300-hPa relative humidity, respectively, from the National Centers for Environmental Prediction (NCEP) reanalyses. A simple empirical model employing the fuel use and the monthly mean 300-hPa temperatures and relative humidities yields a reasonable representation of the seasonal variation in contrail frequency. The interannual drop in contrail frequency coincides with a decrease in mean 300-hPa relative humidities from 45.8% during the first period to 38.2% in 1998–99, one of the driest periods in the NCEP record.

Observations of vertical distributions of moisture and solutes in deset sand in China

(1994). Observations of vertical distributions of moisture and solutes in deset sand in China. SIL Proceedings, 1922-2010: Vol. 25, No. 3, pp. 1455-1455.

On the Relationship Between Scatterometer-Derived Convergences and Atmospheric Moisture

Fields of divergence calculated from the Seasat-A Satellite Scatterometer winds and fields of integrated water vapor and rainrate from the Scanning Multichannel Microwave Radiometer on Seasat are constructed for three different midlatitude cyclones. These storms include an explosively deepening cyclone that occurred in the North Atlantic (also known as the Queen Elizabeth II cyclone), a storm that occurred in the North Pacific, and a Southern Ocean storm. In all three cases, the regions of convergence and atmospheric water (vapor and rain) are consistent with each other and help to define features of each storm. The vertical distribution of moisture is inferred for one case using both the convergence pattern and the integrated water vapor field. In another, interpretation of the convergence field in a data gap region is aided by the water vapor field. In all three cases, surface low pressure centers, fronts, and even frontal waves are clearly evident as areas of convergence, and increased water vapor and rainrate.

Tornado over Punjab

A tornado passed over a few villages in the Ludhiana district in Punjab on 10 March 1975. Synoptic situation and meteorological conditions in relation to the stability of the air column the horizontal and vertical distribution of moisture and the wind flow associated with this tornado have been discussed.