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Nipping frost in the bud

Weather in high-elevation terrain makes northern New Mexico a challenging place to grow an orchard with apples, apricots, cherries or peaches for market. Such a landscape creates significant daily temperature swings with frosts occurring late into the spring, resulting in challenging conditions for fruit growing.

Tirtha Banarjee

Changes in climate patterns add to these challenges. In particular, warm periods arrive earlier in the spring, causing the budding process in fruit trees to start earlier. This leads to two disadvantages for the tree: first, warmer nights can prevent internal processes in plants that harden the buds to withstand late-season frosts. In a compounding effect, the less hardy buds still have to contend with late-season frosts. In Albuquerque and Santa Fe, for example, there is no evidence that the last frost date is moving earlier in the year.

Local fruit growers, such as Chris Bassett of Freshies of New Mexico in Velarde and Tim Seaman of Manzanar Los Silvestres in Abiquiu, watch weather reports and take steps to nurse their orchards through those cold spring nights after the plants have started budding. Using software developed at Los Alamos National Laboratory, work is being done to measure and predict frost events to help farmers such as Bassett and Seaman protect against frost damage, and improve crop health and yield.

This work is funded by the New Mexico Small Business Assistance (NMSBA) program, a state of New Mexico tax credit for national laboratories to assist New Mexico small businesses. The NMSBA program allows for-profit small businesses in New Mexico that are facing a technical challenge to access the unique expertise and capabilities of Los Alamos and Sandia national laboratories at no cost to the company.

Frost damages a plant when its tissue temperature falls below a certain threshold. So the first step in detecting frost damage is to determine if and where this threshold is occurring for all plants at the farm. Scientists do this using atmospheric dynamics and plant biophysics models that take into consideration the complicated processes associated with the carbon, water and the energy cycles of a plant, as well as the local landscape.

The next step of frost damage detection is to understand the localized climatic variations in the immediate vicinity of the farm – its microclimate. The surrounding topography and vegetation, among other factors, influence a microclimate, including how cold air moves and potentially lingers in a specific area.

Kurt Solander

By using weather sensors and instruments to measure factors such as air temperature, wind speed, light availability, atmospheric pressure and relative humidity, researchers are able to monitor and simulate the microclimate of a farm. These simulations are derived from Los Alamos-developed computer models of the atmosphere that are also used to simulate and predict forest fire behavior. That work, in turn, stemmed from fundamental laboratory expertise in supercomputer codes that model how fluids flow under extreme conditions, research that directly supports the lab’s national security mission.

The goal is to combine the measurements and models to identify potential frost-mitigation techniques that can be applied to individual farms. By determining which part of a farm is the coldest, farmers can take better precautions against frost. Current practices at Freshies of New Mexico involve using heaters to warm the air and fans to circulate this air through a partially enclosed greenhouse where the crops are grown. By working with lab scientists, the participating farmers will be better able to identify and address flaws in this system to avoid crop damage and minimize heating costs. Model simulations could also help farmers evaluate the benefits of placing vegetation barriers to create buffer zones between cold air and valuable crops.

Technology is already monitoring Bassett’s orchard in Velarde to understand wind flow and predict the most vulnerable regions of frost damage. The next step is to simulate and understand the exact nature of cold wind flow through surrounding topography and vegetation canopies during cold nights.

The results will be critical in making informed decisions about frost mitigation strategies – and in making sure Northern New Mexicans have plenty of local fruit to enjoy this summer.

For more information about the NMSBA program, visit nmsbaprogram.org.

Tirtha Banerjee is an atmospheric scientist in the Computational Earth Science group at Los Alamos National Laboratory; he studies air flows in complex terrain and atmospheric turbulence, and incorporated a biophysics component to the model. Kurt Solander is a hydrologist in the Computational Earth Science group at Los Alamos. He works with weather instrumentation set-up and model simulations designed to help predict the occurrence of frost at the orchards. Gary Goddard is the team leader for Building Automation and Data Acquisition Systems, where he and Adam Drew implement novel sensors for monitoring of building HVAC systems to improve efficiency.

 

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