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Dr. Laura Harrison
Climate Hazards Center, UC Santa Barbara, Santa Barbara, CA 93106, USA

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Research Keywords & Expertise

0 Hydrology
0 Remote Sensing
0 agroclimatology
0 Drought monitoring and forecasting
0 Climate trends and impacts

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Preprint content
Published: 03 March 2021
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Sparse gauge networks in Sub-Saharan Africa (SSA) limit our ability to identify changing precipitation extremes with in situ observations. Given the potential for satellite and satellite-gauge precipitation products to help, we investigate how daily gridded gauge and satellite products compare for seven core climate change precipitation indices. According to a new gauge-only product, the Rainfall Estimates on a Gridded Network (REGEN), there were notable changes in SSA precipitation characteristics between 1950 and 2013 in well-gauged areas. We examine these trends and how these vary for wet, intermediate, and dry areas. For a 31 year period of overlap, we compare REGEN data, other gridded products and three satellite products. Then for 1998–2013, we compare a set of 12 satellite products. Finally, we compare spatial patterns of 1983–2013 trends across all of SSA. Robust 1950–2013 trends indicate that in well-gauged areas extreme events became wetter, particularly in wet areas. Annual totals decreased due to fewer rain days. Between 1983 and 2013 there were positive trends in average precipitation intensity and annual maximum 1 d totals. These trends only represent 15% of SSA, however, and only one tenth of the main wet areas. Unfortunately, gauge and satellite products do not provide consensus for wet area trends. A promising result for identifying regional changes is that numerous satellite products do well at interannual variations in precipitation totals and number of rain days, even as well as some gauge-only products. Products are less accurate for dry spell length and average intensity and least accurate for annual maximum 1 d totals. Tropical Rainfall Measuring Mission Multi-satellite Precipitation Analysis (3B42-V7) and Climate Hazards center Infrared Precipitation with Stations (CHIRPS v2.0) ranked highest for multiple indices. Several products have seemingly unrealistic trends outside of the well-gauged areas that may be due to influence of non-stationary systematic biases.

Harrison, L., Funk, C., & Peterson, P. (2019). Identifying changing precipitation extremes in Sub-Saharan Africa with gauge and satellite products. Environmental Research Letters, 14(8), 085007. https://doi.org/10.1088/1748-9326/ab2cae

ACS Style

Laura Harrison; Chris Funk; Pete Peterson. Identifying changing precipitation extremes in Sub-Saharan Africa with gauge and satellite products. 2021, 1 .

AMA Style

Laura Harrison, Chris Funk, Pete Peterson. Identifying changing precipitation extremes in Sub-Saharan Africa with gauge and satellite products. . 2021; ():1.

Chicago/Turabian Style

Laura Harrison; Chris Funk; Pete Peterson. 2021. "Identifying changing precipitation extremes in Sub-Saharan Africa with gauge and satellite products." , no. : 1.

Journal article
Published: 29 July 2020 in Remote Sensing
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West Africa represents a wide gradient of climates, extending from tropical conditions along the Guinea Coast to the dry deserts of the south Sahara, and it has some of the lowest income, most vulnerable populations on the planet, which increases catastrophic impacts of low and high frequency climate variability. This paper investigates low and high frequency climate variability in West African monthly and seasonal precipitation and reference evapotranspiration from the early 1980s to 2016. We examine the impact of those trends and how they interact with payouts from index insurance products. Understanding low and high frequency variability in precipitation and reference evapotranspiration at these scales can provide insight into trends during periods critical to agricultural performance across the region. For index insurance, it is important to identify low-frequency variability, which can result in radical departures between designed/planned and actual insurance payouts, especially in the later part of a 30-year period, a common climate analysis period. We find that evaporative demand and precipitation are not perfect substitutes for monitoring crop deficits and that there may be space to use both for index insurance design. We also show that low yields—aligned with the need for insurance payouts—can be predicted using classification trees that include both precipitation and reference evapotranspiration.

ACS Style

S. Blakeley; Stuart Sweeney; Gregory Husak; Laura Harrison; Chris Funk; Pete Peterson; Daniel Osgood. Identifying Precipitation and Reference Evapotranspiration Trends in West Africa to Support Drought Insurance. Remote Sensing 2020, 12, 2432 .

AMA Style

S. Blakeley, Stuart Sweeney, Gregory Husak, Laura Harrison, Chris Funk, Pete Peterson, Daniel Osgood. Identifying Precipitation and Reference Evapotranspiration Trends in West Africa to Support Drought Insurance. Remote Sensing. 2020; 12 (15):2432.

Chicago/Turabian Style

S. Blakeley; Stuart Sweeney; Gregory Husak; Laura Harrison; Chris Funk; Pete Peterson; Daniel Osgood. 2020. "Identifying Precipitation and Reference Evapotranspiration Trends in West Africa to Support Drought Insurance." Remote Sensing 12, no. 15: 2432.

Communication
Published: 21 September 2019 in Water
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Acute and chronic water scarcity impacts four billion people, a number likely to climb with population growth and increasing demand for food and energy production. Chronic water insecurity and long-term trends are well studied at the global and regional level; however, there have not been adequate systems in place for routinely monitoring acute water scarcity. To address this gap, we developed a monthly monitoring system that computes annual water availability per capita based on hydrologic data from the Famine Early Warning System Network (FEWS NET) Land Data Assimilation System (FLDAS) and gridded population data from WorldPop. The monitoring system yields maps of acute water scarcity using monthly Falkenmark classifications and departures from the long-term mean classification. These maps are designed to serve FEWS NET monitoring objectives; however, the underlying data are publicly available and can support research on the roles of population and hydrologic change on water scarcity at sub-annual and sub-national scales.

ACS Style

Amy McNally; Kristine Verdin; Laura Harrison; Augusto Getirana; Jossy Jacob; Shraddhanand Shukla; Kristi Arsenault; Christa Peters-Lidard; James P. Verdin. Acute Water-Scarcity Monitoring for Africa. Water 2019, 11, 1968 .

AMA Style

Amy McNally, Kristine Verdin, Laura Harrison, Augusto Getirana, Jossy Jacob, Shraddhanand Shukla, Kristi Arsenault, Christa Peters-Lidard, James P. Verdin. Acute Water-Scarcity Monitoring for Africa. Water. 2019; 11 (10):1968.

Chicago/Turabian Style

Amy McNally; Kristine Verdin; Laura Harrison; Augusto Getirana; Jossy Jacob; Shraddhanand Shukla; Kristi Arsenault; Christa Peters-Lidard; James P. Verdin. 2019. "Acute Water-Scarcity Monitoring for Africa." Water 11, no. 10: 1968.

Accepted manuscript
Published: 26 June 2019 in Environmental Research Letters
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Sparse gauge networks in Sub-Saharan Africa limit our ability to identify changing precipitation extremes with in situ observations. Given the potential for satellite and satellite-gauge precipitation products to help, we investigate how daily gridded gauge and satellite products compare for seven core climate change precipitation indices. According to a new gauge-only product, the Rainfall Estimates on a Gridded Network (REGEN), there were notable changes in Sub-Saharan Africa precipitation characteristics between 1950 and 2013 in well-gauged areas. We examine these trends and how these vary for wet, intermediate, and dry areas. For a 31-year period of overlap, we compare REGEN data, other gridded products and three satellite products. Then for 1998-2013, we compare a set of 12 satellite products. Finally, we compare spatial patterns of 1983-2013 trends across all of Sub-Saharan Africa. Robust 1950-2013 trends indicate that in well-gauged areas extreme events became wetter, particularly in wet areas. Annual totals decreased due to fewer rain days. Between 1983 and 2013 there were positive trends in average precipitation intensity and annual maximum 1-day totals. These trends only represent 15% of Sub-Saharan Africa, however, and only one tenth of the main wet areas. Unfortunately, gauge and satellite products do not provide consensus for wet area trends. A promising result for identifying regional changes is that numerous satellite products do well at interannual variations in precipitation totals and number of rain days, even as well as some gauge-only products. Products are less accurate for dry spell length and average intensity and least accurate for annual maximum 1-day totals. Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA 3B42-V7) and Climate Hazards center Infrared Precipitation with Stations (CHIRPS v2.0) ranked highest for multiple indices. Several products have seemingly unrealistic trends outside of the well-gauged areas that may be due to influence of non-stationary systematic biases.

ACS Style

Laura Harrison; Chris Funk; Pete Peterson. Identifying changing precipitation extremes in Sub-Saharan Africa with gauge and satellite products. Environmental Research Letters 2019, 14, 085007 .

AMA Style

Laura Harrison, Chris Funk, Pete Peterson. Identifying changing precipitation extremes in Sub-Saharan Africa with gauge and satellite products. Environmental Research Letters. 2019; 14 (8):085007.

Chicago/Turabian Style

Laura Harrison; Chris Funk; Pete Peterson. 2019. "Identifying changing precipitation extremes in Sub-Saharan Africa with gauge and satellite products." Environmental Research Letters 14, no. 8: 085007.

Journal article
Published: 20 February 2019 in International Journal of Climatology
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ACS Style

Laura Harrison; Chris Funk; Amy McNally; Shraddhanand Shukla; Gregory Husak. Pacific sea surface temperature linkages with Tanzania's multi‐season drying trends. International Journal of Climatology 2019, 39, 3057 -3075.

AMA Style

Laura Harrison, Chris Funk, Amy McNally, Shraddhanand Shukla, Gregory Husak. Pacific sea surface temperature linkages with Tanzania's multi‐season drying trends. International Journal of Climatology. 2019; 39 (6):3057-3075.

Chicago/Turabian Style

Laura Harrison; Chris Funk; Amy McNally; Shraddhanand Shukla; Gregory Husak. 2019. "Pacific sea surface temperature linkages with Tanzania's multi‐season drying trends." International Journal of Climatology 39, no. 6: 3057-3075.

Preprint content
Published: 08 February 2019
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In operational analyses of the surface moisture imbalance that defines drought, the supply aspect has generally been well characterized by precipitation; however, the same count be said of the demand side—a function of evaporative demand (E0) and surface moisture availability. In drought monitoring, E0 is often poorly parameterized by a climatological mean, by non-physically based estimates, or is neglected entirely. One problem has been a paucity of driver data—on temperature, humidity, solar radiation, and wind speed—required to fully characterize E0. This deficient E0 modeling is particularly troublesome over data-sparse regions that are also home to drought-vulnerable populations, such as across much of Africa. There is thus urgent need for global E0 estimates for physically accurate drought analyses and food security assessments; further we need an improved understanding of how E0 and drought interact and to exploit these interactions in drought monitoring. In this presentation we explore ways to meet these needs. From MERRA-2—an accurate, fine-resolution land-surface/atmosphere reanalysis—we have developed a >38-year, daily, global Penman-Monteith reference ET dataset as a fully physical metric of E0. This dataset is valuable for examining hydroclimatic changes and extremes. A novel drought index based on this dataset—the Evaporative Demand Drought Index (EDDI)—represents drought’s demand perspective, and permits early warning and ongoing monitoring of agricultural flash drought and hydrologic drought. We highlight the findings of our examination of E0-drought interactions and using EDDI in Africa. Using reference ET as an E0 metric has permitted explicit attribution of the variability of E0 across Africa, and of E0 anomalies associated with canonical droughts in the Sahel region. This analysis determines where, when, and to what relative degree each of the individual drivers of E0 affects the demand side of drought. Using independent estimates of drought across space and time—CHIRPS precipitation and the Normalized Difference Vegetation Index for 1982-2015—we examine the differences between drought and non-drought periods, and between precipitation-forced droughts and droughts forced by a combination of precipitation and E0.

ACS Style

Mike Hobbins; Laura Harrison; Sari Blakeley; Candida Dewes; Greg Husak; Shraddhanand Shukla; Harikishan Jayanthi; Amy McNally; Daniel Sarmiento; James Verdin. Drought in Africa: Understanding and Exploiting the Demand Perspective Using a New Evaporative Demand Reanalysis. 2019, 1 .

AMA Style

Mike Hobbins, Laura Harrison, Sari Blakeley, Candida Dewes, Greg Husak, Shraddhanand Shukla, Harikishan Jayanthi, Amy McNally, Daniel Sarmiento, James Verdin. Drought in Africa: Understanding and Exploiting the Demand Perspective Using a New Evaporative Demand Reanalysis. . 2019; ():1.

Chicago/Turabian Style

Mike Hobbins; Laura Harrison; Sari Blakeley; Candida Dewes; Greg Husak; Shraddhanand Shukla; Harikishan Jayanthi; Amy McNally; Daniel Sarmiento; James Verdin. 2019. "Drought in Africa: Understanding and Exploiting the Demand Perspective Using a New Evaporative Demand Reanalysis." , no. : 1.

Accepted manuscript
Published: 13 June 2018 in Environmental Research Letters
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December-February precipitation in Southern Africa during recent El Niño events is studied by distinguishing circulation and precipitation responses during strong and moderate-to-weak events. We find that while both strong and moderate-to-weak El Niño events tend to dry Southern Africa, the pattern and magnitude of precipitation anomalies in the region are different, with strong El Niño events resulting in rainfall deficits often less than -0.88 standardized units and deficits of only about half that for the moderate-to-weak case. Additionally, the likelihood of Southern Africa receiving less than climatologic precipitation is approximately 80% for strong El Niño events compared to just over 60% for moderate-to-weak El Niño. Strong El Niño events are found to substantially disrupt onshore moisture transports from the Indian Ocean and increase geopotential heights within the Angola Low. Since El Niño is the most predictable component of the climate system that influences Southern Africa precipitation, the information provided by this assessment of the likelihood of dry conditions can serve to benefit early warning systems.

ACS Style

Catherine Pomposi; Chris Funk; Shraddhanand Shukla; Laura Harrison; Tamuka Magadzire. Distinguishing southern Africa precipitation response by strength of El Niño events and implications for decision-making. Environmental Research Letters 2018, 13, 074015 .

AMA Style

Catherine Pomposi, Chris Funk, Shraddhanand Shukla, Laura Harrison, Tamuka Magadzire. Distinguishing southern Africa precipitation response by strength of El Niño events and implications for decision-making. Environmental Research Letters. 2018; 13 (7):074015.

Chicago/Turabian Style

Catherine Pomposi; Chris Funk; Shraddhanand Shukla; Laura Harrison; Tamuka Magadzire. 2018. "Distinguishing southern Africa precipitation response by strength of El Niño events and implications for decision-making." Environmental Research Letters 13, no. 7: 074015.

Journal article
Published: 01 January 2018 in Bulletin of the American Meteorological Society
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ACS Style

Chris Funk; Frank Davenport; Laura Harrison; Tamuka Magadzire; Gideon Galu; Guleid A. Artan; Shraddhanand Shukla; Diriba Korecha; Matayo Indeje; Catherine Pomposi; Denis Macharia; Gregory Husak; Faka Dieudonne Nsadisa. Anthropogenic Enhancement of Moderate-to-Strong El Niño Events Likely Contributed to Drought and Poor Harvests in Southern Africa During 2016. Bulletin of the American Meteorological Society 2018, 99, S91 -S96.

AMA Style

Chris Funk, Frank Davenport, Laura Harrison, Tamuka Magadzire, Gideon Galu, Guleid A. Artan, Shraddhanand Shukla, Diriba Korecha, Matayo Indeje, Catherine Pomposi, Denis Macharia, Gregory Husak, Faka Dieudonne Nsadisa. Anthropogenic Enhancement of Moderate-to-Strong El Niño Events Likely Contributed to Drought and Poor Harvests in Southern Africa During 2016. Bulletin of the American Meteorological Society. 2018; 99 (1):S91-S96.

Chicago/Turabian Style

Chris Funk; Frank Davenport; Laura Harrison; Tamuka Magadzire; Gideon Galu; Guleid A. Artan; Shraddhanand Shukla; Diriba Korecha; Matayo Indeje; Catherine Pomposi; Denis Macharia; Gregory Husak; Faka Dieudonne Nsadisa. 2018. "Anthropogenic Enhancement of Moderate-to-Strong El Niño Events Likely Contributed to Drought and Poor Harvests in Southern Africa During 2016." Bulletin of the American Meteorological Society 99, no. 1: S91-S96.

Journal article
Published: 01 December 2016 in Bulletin of the American Meteorological Society
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ACS Style

Chris Funk; Laura Harrison; Shraddhanand Shukla; Diriba Korecha; Tamuka Magadzire; Gregory Husak; Gideon Galu; Andrew Hoell. Assessing the Contributions of Local and East Pacific Warming to the 2015 Droughts in Ethiopia and Southern Africa. Bulletin of the American Meteorological Society 2016, 97, S75 -S80.

AMA Style

Chris Funk, Laura Harrison, Shraddhanand Shukla, Diriba Korecha, Tamuka Magadzire, Gregory Husak, Gideon Galu, Andrew Hoell. Assessing the Contributions of Local and East Pacific Warming to the 2015 Droughts in Ethiopia and Southern Africa. Bulletin of the American Meteorological Society. 2016; 97 (12):S75-S80.

Chicago/Turabian Style

Chris Funk; Laura Harrison; Shraddhanand Shukla; Diriba Korecha; Tamuka Magadzire; Gregory Husak; Gideon Galu; Andrew Hoell. 2016. "Assessing the Contributions of Local and East Pacific Warming to the 2015 Droughts in Ethiopia and Southern Africa." Bulletin of the American Meteorological Society 97, no. 12: S75-S80.

Journal article
Published: 09 March 2016 in Earth System Dynamics
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The area of leaves in the plant canopy, measured as leaf area index (LAI), modulates key land–atmosphere interactions, including the exchange of energy, moisture, carbon dioxide (CO2), and other trace gases and aerosols, and is therefore an essential variable in predicting terrestrial carbon, water, and energy fluxes. Here our goal is to characterize the LAI projections from the latest generation of earth system models (ESMs) for the Representative Concentration Pathway (RCP) 8.5 and RCP4.5 scenarios. On average, the models project increases in LAI in both RCP8.5 and RCP4.5 over most of the globe, but also show decreases in some parts of the tropics. Because of projected increases in variability, there are also more frequent periods of low LAI across broad regions of the tropics. Projections of LAI changes varied greatly among models: some models project very modest changes, while others project large changes, usually increases. Modeled LAI typically increases with modeled warming in the high latitudes, but often decreases with increasing local warming in the tropics. The models with the most skill in simulating current LAI in the tropics relative to satellite observations tend to project smaller increases in LAI in the tropics in the future compared to the average of all the models. Using LAI projections to identify regions that may be vulnerable to climate change presents a slightly different picture than using precipitation projections, suggesting LAI may be an additional useful tool for understanding climate change impacts. Going forward, users of LAI projections from the CMIP5 ESMs evaluated here should be aware that model outputs do not exhibit clear-cut relationships to vegetation carbon and precipitation. Our findings underscore the need for more attention to LAI projections, in terms of understanding the drivers of projected changes and improvements to model skill.

ACS Style

Natalie Mahowald; Fiona Lo; Yun Zheng; Laura Harrison; Chris Funk; Danica Lombardozzi; Christine Goodale. Projections of leaf area index in earth system models. Earth System Dynamics 2016, 7, 211 -229.

AMA Style

Natalie Mahowald, Fiona Lo, Yun Zheng, Laura Harrison, Chris Funk, Danica Lombardozzi, Christine Goodale. Projections of leaf area index in earth system models. Earth System Dynamics. 2016; 7 (1):211-229.

Chicago/Turabian Style

Natalie Mahowald; Fiona Lo; Yun Zheng; Laura Harrison; Chris Funk; Danica Lombardozzi; Christine Goodale. 2016. "Projections of leaf area index in earth system models." Earth System Dynamics 7, no. 1: 211-229.

Preprint content
Published: 15 April 2015 in Earth System Dynamics Discussions
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The amount of leaves in a plant canopy (measured as leaf area index, LAI) modulates key land–atmosphere interactions, including the exchange of energy, moisture, carbon dioxide (CO2), and other trace gases, and is therefore an essential variable in predicting terrestrial carbon, water, and energy fluxes. The latest generation of Earth system models (ESMs) simulate LAI, as well as provide projections of LAI in the future to improve simulations of biophysical and biogeochemical processes, and for use in climate impact studies. Here we use satellite measurements of LAI to answer the following questions: (1) are the models accurately simulating the mean LAI spatial distribution? (2) Are the models accurately simulating the seasonal cycle in LAI? (3) Are the models correctly simulating the processes driving interannual variability in the current climate? And finally based on this analysis, (4) can we reduce the uncertainty in future projections of LAI by using each model's skill in the current climate? Overall, models are able to capture some of the main characteristics of the LAI mean and seasonal cycle, but all of the models can be improved in one or more regions. Comparison of the modeled and observed interannual variability in the current climate suggested that in high latitudes the models may overpredict increases in LAI based on warming temperature, while in the tropics the models may overpredict the negative impacts of warming temperature on LAI. We expect, however, larger uncertainties in observational estimates of interannual LAI compared to estimates of seasonal or mean LAI. Future projections of LAI by the ESMs are largely optimistic, with only limited regions seeing reductions in LAI. Future projections of LAI in the models are quite different, and are sensitive to climate model projections of precipitation. They also strongly depend on the amount of carbon dioxide fertilization in high latitudes. Based on comparisons between model simulated LAI and observed LAI in the current climate, we can reduce the spread in model future projections, especially in the tropics, by taking into account model skill. In the tropics the models which perform the best in the current climate tend to project a more modest increase in LAI in the future compared to the average of all models. These top performing models also project an increase in the frequency of drought in some regions of the tropics, with droughts being defined as minus one standardized deviation events.

ACS Style

Natalie M Mahowald; Fiona Lo; Yuqing Zheng; Laura Harrison; Chris Funk; Danica Lombardozzi. Leaf Area Index in Earth System Models: evaluation and projections. Earth System Dynamics Discussions 2015, 7, 211 -229.

AMA Style

Natalie M Mahowald, Fiona Lo, Yuqing Zheng, Laura Harrison, Chris Funk, Danica Lombardozzi. Leaf Area Index in Earth System Models: evaluation and projections. Earth System Dynamics Discussions. 2015; 7 (1):211-229.

Chicago/Turabian Style

Natalie M Mahowald; Fiona Lo; Yuqing Zheng; Laura Harrison; Chris Funk; Danica Lombardozzi. 2015. "Leaf Area Index in Earth System Models: evaluation and projections." Earth System Dynamics Discussions 7, no. 1: 211-229.

Journal article
Published: 31 March 2012 in Applied Geography
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Guatemala and Haiti are two of the most food insecure nations in the Western Hemisphere. Measurements of food availability and access are instrumental in developing targeted hunger reduction strategies yet no estimates of cropped area (a critical input in the calculation of food production) at either a national or sub-national-level exist. The purpose of this research is to produce estimates of cropped area for Guatemala and Haiti using an area frame sampling approach and very high resolution (∼1 m) satellite imagery. Related research has combined livelihood data with topographic information to construct cropped area estimates in other settings using generalized additive models. We expand this approach with the inclusion of specific population variables in place of the livelihood data. We produce estimates of cropped area for the two countries and sub-national units and our results highlight the significance and complexity of incorporating explicit population characteristics into models of cropped area.

ACS Style

K. Grace; G.J. Husak; L. Harrison; D. Pedreros; J. Michaelsen. Using high resolution satellite imagery to estimate cropped area in Guatemala and Haiti. Applied Geography 2012, 32, 433 -440.

AMA Style

K. Grace, G.J. Husak, L. Harrison, D. Pedreros, J. Michaelsen. Using high resolution satellite imagery to estimate cropped area in Guatemala and Haiti. Applied Geography. 2012; 32 (2):433-440.

Chicago/Turabian Style

K. Grace; G.J. Husak; L. Harrison; D. Pedreros; J. Michaelsen. 2012. "Using high resolution satellite imagery to estimate cropped area in Guatemala and Haiti." Applied Geography 32, no. 2: 433-440.