NOAA National Centers for Environmental Information
Levant & Central American Climate 
Decoding Vegetation:analyzing drought conditions in desert and rainforest environments 

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>> ALEC: The Levant and Central American regions are repeatedly struck by the disastrous effects of drought 
	and heavy precipitation. Drought frequently impacts the Levant, which includes Lebanon, Israel, 
	Jordan, Syria, and Iraq, and along the Dry Corridor of Central America, consisting of Guatemala, Honduras, 
	El Salvador, and Nicaragua. Stress on water resources has the power to severely reduce agricultural yield 
	and act as a catalyst for civil conflict. Village populations running out of water migrate to urban centers 
	that already fall victim to overpopulation and water stress. The recent Syrian Crisis is an example of 
	competition of resources due to overcrowded cities, leading to disaffection and civil unrest. 


>> MAJOR RYAN HARRIS: The 14th Weather Squadron [is] one of two climate centers in the Department of Defense. Our 
	current drought and precipitation monitoring efforts have really only started over, I would say, the last eighteen
	months. An environmental threat like drought [it] can be seen as a threat multiplier and any area that's already 
	unstable perhaps in terms of their government or their resources...when you throw a drought on top of that, it only
	exacerbates the situation there. Anything that we can do to get a more holistic picture of what drought's doing to 
	a region and the vegetation in that region is a key aspect to the monitoring capabilities we have here on the 
	14th Weather Squadron.

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>> ALEC: Our mission for this project is to enhance the 14th Weather Squadron’s drought monitoring tool by providing them 
	with Normalized Difference Vegetation Index data. Our maps and climatologies of NDVI data will assist the Air Force 
	with predicting areas within the study regions that are vulnerable to climate extremes.

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>>ALEC: Normalized Difference Vegetation Index is a unique measurement of vegetative activity.The data was gathered using NOAA AVHRR sensors 
	and NASA Terra MODIS satellites. NDVI sensors measure the difference between visible and near-infrared sunlight reflected by plants. 
	The percent of visible and near-infrared light reflected determines NDVI, which is calculated using this equation. NDVI values range 
	from -1 to 1 with lower numbers representing low vegetation and high numbers representing high vegetation.

>>ALEC: Our team used NDVI data to create basic climatologies, study seasonality trends and analyze drought years for both regions.
	The products were constructed using R Statistical Programming and ArcGIS software.


>>CHRISTIE: Using NDVI values that were averaged over each month, the team classified the data by 5 vegetation signatures. For the Levant, 
	the majority of the NDVI value ranges were classified as soil, while Central America was primarily classified as shrub & grassland. 
	These classes were subset into high vegetation (Green) and low vegetation (Brown) to analyze typical seasonal and spatial changes 
	in both regions.

>>HAYLEY: We determined the monthly percent differences for years affected by drought events and El Niño. For the Levant region we focused 
	on the detrimental drought from 2007-2010. Looking at the years before and after the drought we saw a decrease in NDVI values from 
	the average, especially in 2008, shown in purple on the map. For Central America we examined the 97-’98 El Nino and compared NDVI 
	value differences to a weak La Nina year. NDVI values during El Nino were much higher than average [indicated by green], especially 
	compared to a weak La Nina.

>>ALEC: Using R statistical analyses we calculated the linear regression of NDVI at each pixel over the 33-year study period and created 
	representative maps. Each trend pixel represents the general change per-year over the 33-year period. 
   
>>ALEC: This project has provided the United States Air Force 14th Weather Squadron with NDVI data, vegetation climatologies, and trends
	analyses to integrate into their current drought monitoring methods. These products can be used in continuing DEVELOP terms to
	identify current and future vulnerabilities. 

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