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Article ; Online: Beyond GRACE: Using Satellite Data for Groundwater Investigations.

Lakshmi, Venkat

2016 Volume 54, Issue 5, Page(s) 615–618

Language	English
Publishing date	2016-09
Publishing country	United States
Document type	Journal Article
ZDB-ID	246212-6
ISSN	1745-6584 ; 0017-467X
ISSN (online)	1745-6584
ISSN	0017-467X
DOI	10.1111/gwat.12444
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Article: Flood Depth Estimation during Hurricane Harvey Using Sentinel-1 and UAVSAR Data

Kundu, Sananda / Lakshmi, Venkat / Torres, Raymond

Remote Sensing. 2022 Mar. 17, v. 14, no. 6

2022

Abstract: In August 2017, Hurricane Harvey was one of the most destructive storms to make landfall in the Houston area, causing loss of life and property. Temporal and spatial changes in the depth of floodwater and the extent of inundation form an essential part ... ...

Abstract	In August 2017, Hurricane Harvey was one of the most destructive storms to make landfall in the Houston area, causing loss of life and property. Temporal and spatial changes in the depth of floodwater and the extent of inundation form an essential part of flood studies. This work estimates the flood extent and depth from LiDAR DEM (light detection and ranging digital elevation model) using data from the Synthetic Aperture Radar (SAR)–Unmanned Aerial Vehicle Synthetic Aperture Radar (UAVSAR) and satellite sensor—Sentinel-1. The flood extent showed a decrease between 29–30 August and 5 September 2017. The flood depths estimated using the DEM were compared with the USGS gauge data and showed a correlation (R²) greater than 0.88. The use of Sentinel-1 and UAVSAR resulted in a daily temporal repeat, which helped to document the changes in the flood area and the water depth. These observations are significant for efficient disaster management and to assist relief organizations by providing spatially precise information for the affected areas.
Keywords	digital elevation models ; disaster preparedness ; floodplains ; hurricanes ; lidar ; satellites ; synthetic aperture radar
Language	English
Dates of publication	2022-0317
Publishing place	Multidisciplinary Digital Publishing Institute
Document type	Article
ZDB-ID	2513863-7
ISSN	2072-4292
ISSN	2072-4292
DOI	10.3390/rs14061450
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Land cover and vegetation carbon stock changes in Greece: A 29-year assessment based on CORINE and Landsat land cover data.

Gemitzi, Alexandra / Albarakat, Reyadh / Kratouna, Foteini / Lakshmi, Venkat

The Science of the total environment

2021 Volume 786, Page(s) 147408

Abstract: Evaluation of carbon sequestration in various land cover types is a valuable tool for environmental policies targeting towards minimization of ... ...

Abstract	Evaluation of carbon sequestration in various land cover types is a valuable tool for environmental policies targeting towards minimization of CO
Language	English
Publishing date	2021-04-29
Publishing country	Netherlands
Document type	Journal Article
ZDB-ID	121506-1
ISSN	1879-1026 ; 0048-9697
ISSN (online)	1879-1026
ISSN	0048-9697
DOI	10.1016/j.scitotenv.2021.147408
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Article: Land cover and vegetation carbon stock changes in Greece: A 29-year assessment based on CORINE and Landsat land cover data

Gemitzi, Alexandra / Albarakat, Reyadh / Kratouna, Foteini / Lakshmi, Venkat

Science of the total environment. 2021 Sept. 10, v. 786

2021

Abstract: Evaluation of carbon sequestration in various land cover types is a valuable tool for environmental policies targeting towards minimization of CO₂ emissions and climate change impacts. For the past few decades, remotely sensed information on land cover ... ...

Abstract	Evaluation of carbon sequestration in various land cover types is a valuable tool for environmental policies targeting towards minimization of CO₂ emissions and climate change impacts. For the past few decades, remotely sensed information on land cover has been used as useful alternative to ground observations and has proved to be a robust tool for studying land use / land cover (LULC) changes. The present work deals with the assessment of land-cover changes in a Mediterranean country - Greece, where expected climate change impacts and desertification risk are stated to be severe. This work focused on the CORINE land cover inventory at a spatial resolution of 100 m from 1990 to 2018 and selected Landsat images at 30 m spatial resolution for 1990, 2000 and 2018. Results indicated that the dominant land-cover changes in Greece over the predefined 29-year period, are related to land transformation from Non-irrigated arable land to Irrigated areas, implying an intensification of agricultural practices. Natural grasslands lose a substantial part of their areas transforming into Sclerophyllus vegetation and Sparsely vegetated areas. Forests gain areas from Transitional woodland-shrub and Olive groves increase their extent indicating an overall transition to woody vegetation. Estimation of Vegetation Carbon Stocks indicated a moderate decrease in the 1990 decade followed by a significant increase up to 2012 and a slight decrease thereafter. Forests of all types are by far the most important carbon sinks. Possible implications of country's recent economic crisis were examined and results indicated that economic welfare of the country seems to favor certain land cover types such as Mixed Forests and Permanently Irrigated land, but also preservation of the Vegetation Carbon Stocks.
Keywords	Landsat ; arable soils ; carbon ; carbon dioxide ; carbon sequestration ; carbon sinks ; climate change ; desertification ; economic crises ; environment ; inventories ; irrigated farming ; irrigation ; land cover ; land use change ; remote sensing ; risk ; Greece ; Mediterranean region
Language	English
Dates of publication	2021-0910
Publishing place	Elsevier B.V.
Document type	Article
Note	NAL-AP-2-clean
ZDB-ID	121506-1
ISSN	1879-1026 ; 0048-9697
ISSN (online)	1879-1026
ISSN	0048-9697
DOI	10.1016/j.scitotenv.2021.147408
Database	NAL-Catalogue (AGRICOLA)

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Article: Identifying relative strengths of SMAP, SMOS-IC, and ASCAT to capture temporal variability

Zhang, Runze / Kim, Seokhyeon / Sharma, Ashish / Lakshmi, Venkat

Remote sensing of environment. 2021 Jan., v. 252

2021

Abstract: This study evaluates the relative strengths of three remotely sensed soil moisture (SM) products to capture temporal variability at a global scale, the products being the Soil Moisture Active Passive (SMAP), Soil Moisture Ocean Salinity INRA-CESBIO (SMOS- ...

Abstract	This study evaluates the relative strengths of three remotely sensed soil moisture (SM) products to capture temporal variability at a global scale, the products being the Soil Moisture Active Passive (SMAP), Soil Moisture Ocean Salinity INRA-CESBIO (SMOS-IC) and Advanced Scatterometer (ASCAT). For this, the conventional reference-based Pearson correlation (R) and a statistical technique called Triple Collocation (TC)-based R are calculated. In addition, two alternatives for linear combination of the three data sources for maximizing R against the truth are evaluated, the first using a reference product (i.e. assumed truth) and the second based on TC where three data sources are combined without the need for an underlying reference or assumed truth. The estimated optimal combination weights represent quantitative contributions of the three products in forming the new combined product having the maximized R. Two reanalysis products: the European Centre for Medium-Range Forecast (ECMWF) Interim product (ERA-Interim) and the Modern-Era Retrospective Analysis for Research and Application Land version 2 reanalysis product (MERRA2), are used as the references as well as data alternatives to calculate the conventional reference-based R and the TC-based R combinations. Both types of R, and their derived optimal weights are then compared globally and analyzed under various climate, land cover, and vegetation conditions. Despite the differences between the conventional R and the TC-based R, both metrics displayed consistent spatial distributions and can reflect the temporal variations of each studied dataset without considerable impact from adopted references. All products had difficulty in retrieving SM over arid and polar regions while exhibiting good performance in areas such as South America and Australia. While ASCAT presented higher R values over tropical, savannas, and the vegetation water content interval of 2–5 kg/m², SMAP and SMOS-IC displayed overall comparable and continually high temporal performances across almost all conditions. In the case of the derived optimal weights, a global complementarity of the areas was observed where each satellite-based observation product showed its respective advantage in capturing SM variations in different geographic areas.
Keywords	climate ; data collection ; environment ; land cover ; remote sensing ; retrospective studies ; salinity ; satellites ; soil water ; temporal variation ; water content ; Australia ; South America
Language	English
Dates of publication	2021-01
Publishing place	Elsevier Inc.
Document type	Article
Note	NAL-AP-2-clean
ZDB-ID	431483-9
ISSN	0034-4257
ISSN	0034-4257
DOI	10.1016/j.rse.2020.112126
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Article: Global Dynamics of Stored Precipitation Water in the Topsoil Layer From Satellite and Reanalysis Data

Kim, Hyunglok / Lakshmi, Venkat

Water resources research. 2019 Apr., v. 55, no. 4

2019

Abstract: The amount of soil water in the topsoil layer (from 0 to 10 cm) has been regarded as a key factor in controlling land‐atmosphere interaction by determining the fraction of net radiation. In the present study, we investigate spatial trends of the stored ... ...

Abstract	The amount of soil water in the topsoil layer (from 0 to 10 cm) has been regarded as a key factor in controlling land‐atmosphere interaction by determining the fraction of net radiation. In the present study, we investigate spatial trends of the stored precipitation fraction in the topsoil layer for varying vegetation and aridity indices by utilizing four satellites and two reanalysis data sets on a global scale. Using the Budyko framework, we relate climate regimes to the stored precipitation fraction on a global scale. A positive relation between the stored precipitation fraction with aridity index and a negative relation between the stored precipitation fraction and free parameter, vegetation optical depth, and isohydric slope are discovered. Even though the stored precipitation fraction values were calculated from different soil moisture and precipitation sources, they share an similar spatial trend: the drier and less vegetated the soil is, the more precipitation is retained in the top layer of the soil. Specifically, the topsoil retains 37% ± 11% of precipitated water three days after a rainfall event where the aridity index was greater than 5. Over wet and forest areas, due to large runoff fluxes and plants intercepting water before the precipitated water reached the ground, the topsoil retains 21% ± 2% of precipitated water three days after a rainfall event. Furthermore, by using the modeled data sets in the calculation of the stored precipitation fraction metric, we are able to conduct a sensitivity analysis of FP(f) metrics with respect to different sampling frequency values.
Keywords	climate ; dry environmental conditions ; forests ; net radiation ; rain ; research ; runoff ; satellites ; soil water ; topsoil
Language	English
Dates of publication	2019-04
Size	p. 3328-3346.
Publishing place	John Wiley & Sons, Ltd
Document type	Article
Note	JOURNAL ARTICLE
ZDB-ID	5564-5
ISSN	1944-7973 ; 0043-1397
ISSN (online)	1944-7973
ISSN	0043-1397
DOI	10.1029/2018WR023166
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Evaluating Renewable Groundwater Stress with GRACE Data in Greece.

Gemitzi, Alexandra / Lakshmi, Venkat

Ground water

2018 Volume 56, Issue 3, Page(s) 501–514

Abstract: Groundwater is a resilient water source and its importance is even greater in periods of drought. Areas such as the Mediterranean where adverse climate change effects are expected are bell-weather locations for groundwater depletion and are of ... ...

Abstract	Groundwater is a resilient water source and its importance is even greater in periods of drought. Areas such as the Mediterranean where adverse climate change effects are expected are bell-weather locations for groundwater depletion and are of considerable interest. The present study evaluates renewable groundwater stress (RGS) as the ratio of groundwater use to groundwater availability, quantifying use as the trend in gravity recovery and climate experiment-derived (GRACE) subsurface anomalies (ΔGW
MeSH term(s)	Agriculture ; Climate Change ; Conservation of Natural Resources ; Greece ; Groundwater ; Humans ; Water Supply ; Weather
Language	English
Publishing date	2018
Publishing country	United States
Document type	Case Reports
ZDB-ID	246212-6
ISSN	1745-6584 ; 0017-467X
ISSN (online)	1745-6584
ISSN	0017-467X
DOI	10.1111/gwat.12591
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Article: Simulation of carbon dioxide mineralization and its effect on fault leakage rates in the South Georgia rift basin, southeastern U.S

Alshammari, Adil / Lakshmi, Venkat / Brantley, Duke / Knapp, Camelia C. / Knapp, James H.

Heliyon. 2022 June, v. 8, no. 6

2022

Abstract: Over the past few decades, measured levels of atmospheric carbon dioxide have substantially increased. One of the ways to limit the adverse impacts of increased carbon dioxide concentrations is to capture and store it inside Earth's subsurface, a process ...

Abstract	Over the past few decades, measured levels of atmospheric carbon dioxide have substantially increased. One of the ways to limit the adverse impacts of increased carbon dioxide concentrations is to capture and store it inside Earth's subsurface, a process known as CO₂ sequestration. The success of this method is critically dependent on the ability to confine injected CO₂ for up to thousands of years. Establishing effective maintenance of sealing systems of reservoirs is of importance to prevent CO₂ leakage. In addition, understanding the nature and rate of potential CO₂ leakage related to this injection process is essential to evaluating seal effectiveness and ultimately mitigating global warming. In this study, we evaluated the impact of common chemical reactions between CO₂ and subsurface materials in situ as well as the relationship between CO₂ plume distribution and the CO₂ leakage within the seal zone that cause mineralization. Using subsurface seismic data and well log information, a three-dimensional model consisting of a reservoir and seal zones was created and evaluated for the South Georgia Rift (SGR) basin in the southeastern U.S. The Computer Modeling Group (CMG, 2017), was used to model the effect of CO₂ mineralization on the optimal values of fault permeability permeabilitydue to fluid substitution between the formation water and CO₂. The model simulated the chemical reactions between carbon dioxide and mafic minerals to produce stable minerals of carbonate rock that form in the fault. Preliminary results show that CO₂ migration can be controlled effectively for fault permeability values between 0.1-1 mD. Within this range, mineralization effectively reduced CO₂ leakage within the seal zone.
Keywords	basins ; carbon dioxide ; carbonate rocks ; computers ; geophysical logging ; geophysics ; mineralization ; models ; permeability ; seals ; Georgia
Language	English
Dates of publication	2022-06
Publishing place	Elsevier Ltd
Document type	Article
ZDB-ID	2835763-2
ISSN	2405-8440
ISSN	2405-8440
DOI	10.1016/j.heliyon.2022.e09635
Database	NAL-Catalogue (AGRICOLA)

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Article: A global 1‐km downscaled SMAP soil moisture product based on thermal inertia theory

Fang, Bin / Lakshmi, Venkat / Cosh, Michael / Liu, Pang‐Wei / Bindlish, Rajat / Jackson, Thomas J.

Vadose zone journal. 2022 Mar., v. 21, no. 2

2022

Abstract: Microwave remote sensing technology has been applied to produce soil moisture (SM) retrievals on a global scale for various studies and applications. However, due to the limitations of current technology, the native spatial resolution of currently ... ...

Abstract	Microwave remote sensing technology has been applied to produce soil moisture (SM) retrievals on a global scale for various studies and applications. However, due to the limitations of current technology, the native spatial resolution of currently available passive microwave SM products is on the order of tens of kilometers, and this resolution cannot be used to characterize SM variability on a regional scale. To overcome this limitation, a downscaling algorithm based on the thermal inertia theory–derived relationship between SM and temperature difference was developed using outputs from the Global Land Data Assimilation System–Noah Land Surface Model and the land long‐term data record–Advanced Very High Resolution Radiometer normalized difference vegetation index (NDVI) dataset and applied to the Aqua Moderate Resolution Imaging Spectroradiometer land surface temperature/NDVI data to produce a downscaled 1‐km Soil Moisture Active Passive (SMAP) radiometer daily SM product, respectively, at 6:00 a.m. and 6:00 p.m. on a global scale from 2015 to 2020. The evaluation results reveal that the downscaling model performs better in the middle or low latitudes than in high latitudes. It also performs better in warm months than in cold months. The in situ SM observations from dense networks around the world were used to validate the 1‐km and enhanced 9‐km SMAP SM data. The validation metrics indicated that both the 1‐km and 9‐km SM data have overall overestimation trends, and the unbiased RMSE (0.063 m³ m–³ on average), mean absolute error (0.052 m³ m–³ on average), and spatial standard deviation (0.025 m³ m–³ on average) of the 1 km data are generally more accurate than the metrics of the 9‐km SM data, which indicates that the downscaled data provide reliable observed SM information.
Keywords	algorithms ; cold ; data collection ; models ; satellites ; soil water ; standard deviation ; surface temperature ; vadose zone
Language	English
Dates of publication	2022-03
Publishing place	John Wiley & Sons, Ltd
Document type	Article
Note	JOURNAL ARTICLE
ZDB-ID	2088189-7
ISSN	1539-1663
ISSN	1539-1663
DOI	10.1002/vzj2.20182
Database	NAL-Catalogue (AGRICOLA)

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Article: Comparing Precipitation during Typhoons in the Western North Pacific Using Satellite and In Situ Observations

Sutton, Jessica R. P. / Jakobsen, Alexandra / Lanyon, Kathryn / Lakshmi, Venkat

Remote Sensing. 2022 Feb. 12, v. 14, no. 4

2022

Abstract: Typhoons are known for causing heavy precipitation, very strong winds, and storm surges. With climate change, the occurrence, strength, and duration of typhoons are changing. Daily, weekly, and monthly precipitation from in situ stations from the NOAA ... ...

Abstract	Typhoons are known for causing heavy precipitation, very strong winds, and storm surges. With climate change, the occurrence, strength, and duration of typhoons are changing. Daily, weekly, and monthly precipitation from in situ stations from the NOAA Global Historical Climatological Network (GHCN) were compared in the Western North Pacific from 2000 to 2018 against two widely used datasets: NASA’s TRMM TMPA and PERSIANN-CDR. Additionally, precipitation levels during twenty-five typhoons were compared using precipitation estimates. There have been reductions in the average number of typhoons per year from 1959 to present and by month during the months of August, September, and October. Satellite-derived precipitation estimates from PERSIANN and TRMM TMPA explained approximately 50% of the variation in weekly cumulative precipitation and approximately 72% of the variation in monthly cumulative precipitation during the study period (March 2000–December 2018) when using all available stations. When analysis was completed using only stations close to the best track for the entire duration of a typhoon, 62% of the variation was explained, which is comparable to the weekly and monthly cumulative comparisons. However, most of the stations available and with sufficient data were not located in the tracks of the typhoons. It is of utmost importance to better understand typhoon events by utilizing precipitation data from satellite remote sensing in the Western North Pacific.
Keywords	atmospheric precipitation ; climate change ; data collection ; satellites ; typhoons
Language	English
Dates of publication	2022-0212
Publishing place	Multidisciplinary Digital Publishing Institute
Document type	Article
ZDB-ID	2513863-7
ISSN	2072-4292
ISSN	2072-4292
DOI	10.3390/rs14040877
Database	NAL-Catalogue (AGRICOLA)

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