Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model [presentation]

The purpose of this paper is to provide a comprehensive presentation and interpretation of the Ensemble Kalman Filter (EnKF) and its numerical implementation. The EnKF has a large user group, and numerous publications have discussed applications and theoretical aspects of it. This paper reviews the important results from these studies and also presents new ideas and alternative interpretations which further explain the success of the EnKF. In addition to providing the theoretical framework needed for using the EnKF, there is also a focus on the algorithmic formulation and optimal numerical implementation. A program listing is given for some of the key subroutines. The paper also touches upon specific issues such as the use of nonlinear measurements, in situ profiles of temperature and salinity, and data which are available with high frequency in time. An ensemble based optimal interpolation (EnOI) scheme is presented as a cost-effective approach which may serve as an alternative to the EnKF in some applications. A fairly extensive discussion is devoted to the use of time correlated model errors and the estimation of model bias.

The Ensemble Kalman Filter: Theoretical formulation and practical implementation

In this paper, we examine the role of polarimetry in synthetic aperture radar (SAR) interferometry. We first propose a general formulation for vector wave interferometry that includes conventional scalar interferometry as a special case. Then, we show how polarimetric basis transformations can be introduced into SAR interferometry and applied to form interferograms between all possible linear combinations of polarization states. This allows us to reveal the strong polarization dependency of the interferometric coherence. We then solve the coherence optimization problem involving maximization of interferometric coherence and formulate a new coherent decomposition for polarimetric SAR interferometry that allows the separation of the effective phase centers of different scattering mechanisms. A simplified stochastic scattering model for an elevated forest canopy is introduced to demonstrate the effectiveness of the proposed algorithms. In this way, we demonstrate the importance of wave polarization for the physical interpretation of SAR interferograms. We investigate the potential of polarimetric SAR interferometry using results from the evaluation of fully polarimetric interferometric shuttle imaging radar (SIR)-C/X-SAR data collected during October 8-9, 1994, over the SE Baikal Lake Selenga delta region of Buriatia, Southeast Siberia, Russia.

Polarimetric SAR interferometry

Complete optical absorption and fluorescence spectra were collected for a diverse suite of 0.2-μm-filtered marine, riverine, and estuarine waters, as well as for colored dissolved organic matter (CDOM) isolated from several of these waters by solid-phase C 18 extraction. Absorption and fluorescence parameters for these samples are reported. For surface waters, variations in the fluorescence quantum yields obtained with 355- and 337-nm excitation fell within a narrow window (< 2.5-fold variation about the mean values), demonstrating that fluorescence measurements can be used to determine absorption coefficients of CDOM in the ultraviolet region with reasonably good accuracy. Methods for predicting absorption coefficients and line shapes from the fluorescence data are introduced and tested. The absorption and fluorescence spectra of CDOM extracted from some seawaters differed significantly from those of the original waters, demonstrating that material isolated by hydrophobic adsorption is not necessarily representative of the suite of colored organic matter present in aquatic systems. These results clearly illustrate that great care must be taken when extracted material is used to infer the optical properties of natural waters

Optical absorption and fluorescence properties of chromophoric dissolved organic matter in natural waters

The ultimate source of water for plants is precipitation; rain falling upon soil penetrates it at a rate depending upon the physical properties of that particular soil; snow and hail do the same after melting. If the rate of rainfall or the rate of production of water by melting exceeds the infiltration rate, then surface runoff occurs and the excess water drains into streams and eventually reaches the sea. That water which penetrates the soil replenishes the soil reservoir and when this is filled to capacity (see chapter 3) the surplus drains through into the aquifers. These are strata such as sand or chalk which can hold substantial quantities of recoverable water. Water held in the soil reservoir is drawn into plant roots and up their stems to be evaporated from the leaves back into the atmosphere, where it rejoins water evaporated from the sea, lakes and rivers and from the surface of wet soil. This so-called hydrological cycle (figure 1.2) depends for its continuance upon energy derived from the sun’s radiation and as will be shown in later chapters its rate is governed largely by meteorological factors.

The Water Balance

A review of remote sensing applications in agriculture for food security: Crop growth and yield, irrigation, and crop losses

Quantifying the isolated and integrated impacts of land use (LU) and climate change on streamflow is challenging as well as crucial to optimally manage water resources in river basins. This paper presents a simple hydrologic modeling-based approach to segregate the impacts of land use and climate change on the streamflow of a river basin. The upper Ganga basin (UGB) in India is selected as the case study to carry out the analysis. Streamflow in the river basin is modeled using a calibrated variable infiltration capacity (VIC) hydrologic model. The approach involves development of three scenarios to understand the influence of land use and climate on streamflow. The first scenario assesses the sensitivity of streamflow to land use changes under invariant climate. The second scenario determines the change in streamflow due to change in climate assuming constant land use. The third scenario estimates the combined effect of changing land use and climate over the streamflow of the basin. Based on the results obtained from the three scenarios, quantification of isolated impacts of land use and climate change on streamflow is addressed. Future projections of climate are obtained from dynamically downscaled simulations of six general circulation models (GCMs) available from the Coordinated Regional Downscaling Experiment (CORDEX) project. Uncertainties associated with the GCMs and emission scenarios are quantified in the analysis. Results for the case study indicate that streamflow is highly sensitive to change in urban areas and moderately sensitive to change in cropland areas. However, variations in streamflow generally reproduce the variations in precipitation. The combined effect of land use and climate on streamflow is observed to be more pronounced compared to their individual impacts in the basin. It is observed from the isolated effects of land use and climate change that climate has a more dominant impact on streamflow in the region. The approach proposed in this paper is applicable to any river basin to isolate the impacts of land use change and climate change on the streamflow.

/pdf/isolating-the-impacts-of-land-use-and-climate-change-on-jagf3uq6ue.pdf

Isolating the impacts of land use and climate change on streamflow

https://par.nsf.gov/servlets/purl/10184223

A review of remote sensing applications for water security: Quantity, quality, and extremes

 Reliable estimates of extreme rainfall events are necessary for an accurate prediction of floods Most of the global rainfall products are available at a coarse resolution, rendering them less desirable for extreme rainfall analysis Therefore, regional mesoscale models such as the advanced research version of the Weather Research and Forecasting (WRF) model are often used to provide rainfall estimates at fine grid spacing Modelling heavy rainfall events is an enduring challenge, as such events depend on multi-scale interactions, and the model configurations such as grid spacing, physical parameterization and initialization With this background, the WRF model is implemented in this study to investigate the impact of different processes on extreme rainfall simulation, by considering a representative event that occurred during 15–18 June 2013 over the Ganga Basin in India, which is located at the foothills of the Himalayas This event is simulated with ensembles involving four different microphysics (MP), two cumulus (CU) parameterizations, two planetary boundary layers (PBLs) and two land surface physics options, as well as different resolutions (grid spacing) within the WRF model The simulated rainfall is evaluated against the observations from 18 rain gauges and the Tropical Rainfall Measuring Mission Multi-Satellite Precipitation Analysis (TMPA) 3B42RT version 7 data From the analysis, it should be noted that the choice of MP scheme influences the spatial pattern of rainfall, while the choice of PBL and CU parameterizations influences the magnitude of rainfall in the model simulations Further, the WRF run with Goddard MP, Mellor–Yamada–Janjic PBL and Betts–Miller–Janjic CU scheme is found to perform best in simulating this heavy rain event The selected configuration is evaluated for several heavy to extremely heavy rainfall events that occurred across different months of the monsoon season in the region The model performance improved through incorporation of detailed land surface processes involving prognostic soil moisture evolution in Noah scheme compared to the simple Slab model To analyse the effect of model grid spacing, two sets of downscaling ratios – (i) 1 : 3, global to regional (G2R) scale and (ii) 1 : 9, global to convection-permitting scale (G2C) – are employed Results indicate that a higher downscaling ratio (G2C) causes higher variability and consequently large errors in the simulations Therefore, G2R is adopted as a suitable choice for simulating heavy rainfall event in the present case study Further, the WRF-simulated rainfall is found to exhibit less bias when compared with the NCEP FiNaL (FNL) reanalysis data

/pdf/assessment-of-the-weather-research-and-forecasting-wrf-model-30za35wbvn.pdf

Ila Chawla

Papers

A review of remote sensing applications in agriculture for food security: Crop growth and yield, irrigation, and crop losses

Isolating the impacts of land use and climate change on streamflow

A review of remote sensing applications for water security: Quantity, quality, and extremes

Assessment of the Weather Research and Forecasting (WRF) model for simulation of extreme rainfall events in the upper Ganga Basin

Partitioning uncertainty in streamflow projections under nonstationary model conditions