Posts Tagged: cooling
Why and How to Cool Avocado Trees
If you missed the recent UC/CAS/CAC grower meeting on cooling avocado trees or just want to review the enormous amount of information or just want to wander other grower's orchards, Here is the video of the presentations:
Mitigating Heat
overhead irrigation 2
And Human Heat Stress
Cal/OSHA HEAT ADVISORY
When employees work in hot conditions, employers must take special precautions in order to prevent heat illness. Heat illness can progress to heat stroke and be fatal, especially when emergency treatment is delayed. An effective approach to heat illness is vital to protecting the lives of California workers.
California law requires employers to identify and evaluate workplace hazards and take the steps necessary to address them. The risk of heat illness can be significantly reduced by consistently following just a few simple steps. Employers of outdoor workers at temporary work locations must be particularly alert and also plan for providing first aid and emergency medical services should they become necessary. All workers should be accounted for during and at the end of the work shift. Heat illness results from a combination of factors including environmental temperature and humidity, direct radiant heat from the sun or other sources, air speed, and workload. Personal factors, such as age, weight, level of fitness, medical condition, use of medications and alcohol, and acclimatization effect how well the body deals with excess heat.
Heat Illness Risk Reduction
1. Recognize the Hazard. There is no absolute cut-off below which work in heat is not a risk. With heavy work at high relative humidity or if workers are wearing protective clothing, even work at 70oF can present a risk. In the relative humidity levels often found in hot areas of California (20 to 40 percent) employers need to take some actions to effectively reduce heat illness risk when temperatures approach 80 F. At temperatures above 90 F, especially with heavy work, heat risk reduction needs to be a major concern.
2. Water. There must be an adequate supply of clean, cool, potable water. Employees who are working in the heat need to drink 3-4 glasses of water per hour, including at the start of the shift, in order to replace the water lost to sweat. For an eight-hour day this means employers must provide two or more gallons per person. Thirst is an unreliable indicator of dehydration. Employees often need ongoing encouragement to consume adequate fluids, especially when the workload or process does not encourage breaks.
3. Shade. The direct heat of the sun can add as much as 15 degrees to the heat index. If possible, work should
be performed in the shade. If not, employers where possible, should provide a shaded area for breaks and when employees need relief from the sun. Wide brimmed hats can also decrease the impact of direct heat.
- Acclimatization. People need time for their bodies to adjust to working in heat. This “acclimatization” is particularly important for employees returning to work after (1) a prolonged absence, (2) recent illness, or (3) recently moving from a cool to a hot climate. For heavy work under very hot conditions, a period of 4 to 10 days of progressively increasing work time starting with about 2 hours work per day under the working conditions is recommended. For less severe conditions at least the first 2 or 3 days of work in the heat should be limited to 2 to 4 hours. Monitor employees closely for signs and symptoms of heat illness, particularly when they have not been working in heat for the last few days, and when a heat wave occurs.
- Rest Breaks. Rest breaks are important to reduce internal heat load and provide time for cooling. Heat illness occurs due to a combination of environmental and internal heat that cannot be adequately dissipated. Breaks should be taken in cooler, shaded areas. Rest breaks also provide an opportunity to drink water.
- Prompt Medical Attention. Recognizing the symptoms of heat illness and providing an effective response requires promptly acting on early warning signs. Common early symptoms and signs of heat illness include headache, muscle cramps, and unusual fatigue. However, progression to more serious illness can be rapid and can include unusual behavior, nausea/vomiting, weakness, rapid pulse excessive sweating or hot dry skin, seizures, and fainting or loss of consciousness. Any of these symptoms require immediate attention.
Even the initial symptoms may indicate serious heat exposure. If medical personnel are not immediately available on-site, and you suspect severe heat illness, you must call 911.
Regardless of the worker's protests, no employee with any of the symptoms of possible serious heat illness noted above should be sent home or left unattended without medical assessment and authorization.
7. Training. Supervisors and employees must be trained in the risks of heat illness, and the measures to protect themselves and their co-workers. Training should include:
- Why it is important to prevent heat illness
- Procedures for acclimatization
- The need to drink approximately one quart per hour of water to replace fluids.
- The need to take breaks out of the heat
- How to recognize the symptoms of heat illness
- How to contact emergency services, and how to effectively report the work location to 911.
sun stress
Science Tuesday: Going Nuclear
Reposted from the Fire Adapted Communities Learning Network
On Labor Day weekend, my friends and I canceled a vacation rental on the Trinity River because of the heat and smoke. It was predicted to be 112 degrees inland that weekend, and we figured we'd be crazy to subject ourselves (and our posse of toddlers) to that when we could stay on the coast and enjoy fresh air and cool temperatures. Smart, right?
Saturday morning, we made breakfast at my friend's house and watched the temperature climb. By 10 a.m., it was over 80 degrees, and by noon, it was nearing 100 — unbelievably hot for our foggy redwood coast. And on top of the heat, it was the smokiest I've ever seen it here. Turns out, we hadn't escaped the heat or the smoke.
But here's the weird thing: the inland areas, which were predicted to be unusually hot that weekend, were actually cooler than the coast. My husband, who was working on the Eclipse Complex in the Klamath Mountains — in the heart of the projected heat wave — experienced a high in the low 80s that weekend. Meanwhile, we were grappling with almost unprecedented heat here by the ocean. To have a double-digit difference in temperature between the inland areas and the coast is the norm here, but the coast is never the hotter of the two.
The odd temperature patterns that weekend reminded me of an old paper I read years ago — something about the cooling effects of forest fire smoke, and the potential to use wildfires to better understand the potential impacts of “nuclear winter.” An odd topic, but intriguing, too.
Interestingly, in looking back at the paper, I realized that it was based on data collected in the Klamath Mountains exactly thirty years before this year's hot, smoky Labor Day weekend. The author, Alan Robock, analyzed surface temperature data from weather stations across northern California and southern Oregon, and he found that smoke from nearby wildfires had significant cooling effects in the Klamath River canyon in September of 1987 — temperatures were more than 27 degrees below normal for an entire week and more than 9 degrees cooler than normal for most of the month. During that time, the combination of an inversion and wildfire smoke created a positive feedback loop: smoke trapped by the inversion cooled the surface air temperature, which strengthened the inversion and trapped even more smoke. Of course, the smoke did more than cool the air that month; Robock notes that it also caused severe respiratory problems for people who were living in that area, and even caused tomato plants to shrivel up and die.
More recent studies show other important effects of temperature inversions. Earlier this year, Becky Estes and others published a paper in Ecosphere that looked at the factors influencing fire severity in the Klamath Mountains in 2006 — a year that had moderate burning conditions and is thus representative of years when wildfires might be managed for resource benefit. Of all the weather variables they looked at, temperature inversions had the strongest influence on fire severity that year. Earlier work by Miller et al. (2012) had noted similar patterns, including more surface fire and less crowning under inversions. 1987 and 2008, two of the biggest fire years in our region in the last several decades, had lower than average fire severities thanks to widespread temperature inversions.
Collectively, these studies reveal interesting tensions between humans and fire — not just here in the Klamath Mountains, but everywhere. In some ways, the inversions and smoke are producing conditions we want to see on the ground: lower fire intensities, cooler temperatures, etc. But these can come at the cost of unlivable air quality (not to mention stunted vegetables and wine that tastes like smoke!). And this isn't just about inversions — it's really about us finding ways to live in the crossfire of the natural checks and balances of these systems. We know that we need more fire, and that we need to take advantage of moderate burning conditions, even if that means more smoke. We just need to find good ways to do it — that's what fire adaptation is all about. (Also, I'd be lying if I said Robock's thoughts on nuclear winter didn't seem a little more relevant now than they did last time I read that paper … might be worth revisiting!)
References
Estes, B. L., Knapp, E. E., Skinner, C. N., Miller, J. D., & Preisler, H. K. (2017). Factors Influencing Fire Severity Under Moderate Burning Conditions in the Klamath Mountains, Northern California, USA. Ecosphere, 8(5).
Miller, J. D., Skinner, C. N., Safford, H. D., Knapp, E. E., & Ramirez, C. M. (2012). Trends and Causes of Severity, Size, and Number of Fires in Northwestern California, USA. Ecological Applications, 22(1), 184-203.
Robock, A. (1988). Enhancement of Surface Cooling Due to Forest Fire Smoke. Science, 242, 911-913.
/h2>F. Gordon Mitchell's Impact on Postharvest Technology and California Agriculture
By Mary Lu Arpaia
My association with Gordon goes back nearly 35 years to some of the very earliest days as a new graduate student here in Davis. Sometimes the best things that happen to you are unplanned. That is how I first met Gordon. I had been accepted into graduate school in the Pomology Department but did not have the grades to be offered an assistantship; instead I was offered work study. I went to the work study office and found a job posting in the Pomology Department to work in postharvest. Now, I had planned to do something in the field, but needed a job to pay the bills. And I wanted a job in the department that I had been accepted to as a graduate student. That job was working for Gordon and that was serendipity. When I think back on that one event I know it was one of the most important events in my graduate career and subsequent adventures in life. My experiences with him during my 5 years at Davis have served as the guideposts for my career.
By the time that I was hired to work for Gordon in the Fall of 1977 he was already a respected postharvest biologist. He had gone from the ranks of Farm Advisor to statewide specialist for postharvest. He had achieved a Masters from Cornell University on the effect of controlled atmosphere on apples. His work with forced air cooling and packaging with Rene Giullou and Ed Maxie as well as others had established him to be a leader, albeit a soft spoken one, in the field of postharvest handling. He had just returned from a six month sabbatical in South Africa. He would go on to make more valuable achievements to the California fruit industries as well as worldwide. This included being a co-founder of the very successful UC Davis postharvest shortcourse in 1978 alongside with Adel Kader, Bob Kasmire, Michael Reid and Jim Thompson. His contributions to the California stone fruit industry were recognized by all and culminated by the naming of the postharvest laboratory at the UC Kearney Agricultural Center as the F. G. Mitchell Postharvest Laboratory following the generous donation of his friend LeRoy Giannini.
His dear friend Gawie Eksteen, who worked with him in South Africa during that 1976-77 sabbatical leave wrote this to me. He summarizes so well Gordon’s impact upon the world of postharvest biology:
"Gordon was talented in many ways. He was a master in explaining intricate scientific concepts in such a way that both researchers and growers clearly understood every concept. He was also a “down to earth” scientist, combining technology and practical application. He is still regarded as the father of Forced Air Cooling of fresh produce in South Africa. His contributions in handling and cooling of fresh produce made a tremendous impact on fruit quality in the local and overseas markets. These practical concepts are still most efficient and became the international standard in all fruit, vegetable and flower producing countries."
Adel Kader from the UC Davis Pomology Department (now the Department of Plant Sciences) frequently teamed with Gordon Mitchell on numerous projects including the founding of the Postharvest Technology Program and they worked together as co-editors of the “Perishables Handling Newsletter” for more than 25 years. Adel went on to say,
"Gordon worked collaboratively with colleagues from the Biological and Agricultural Engineering Department to produce the UC Davis Cooling Manual in 1972 and several updated editions during his career. He conducted excellent, mission-oriented research on optimal harvesting and handling of many fruits, including stone fruits, pears, apples, and kiwifruits, that benefited the respective industries not only in California, but throughout the world. His extension program was exemplary and he was recognized internationally as a leader in postharvest biology and technology of fruits."
Jim Thompson, from the Department of Biological and Agricultural Engineering at UC Davis and who also collaborated with Mitchell on numerous projects, said the following,
"Gordon was a pioneer in postharvest technology and a person who worked tirelessly with the California industry to improve the market quality of our fresh fruits and tree nuts. He developed the early concepts and standards for handling California Granny Smith and Fuji apples, kiwifruit, and pistachio nuts. When the tree fruit industry had questions about postharvest issues, their first phone call was to Gordon."
Gordon was comfortable in his own skin. When I remember him I think of the word “ethical”, with high moral standards and integrity; calm, observant, forward-thinking, caring and humorous. He was always there for me as a student and later as a professional. He was an excellent mentor and immediately accepted me as a member of the “Mitchell team” alongside his long time technical support colleague, Gene Mayer. He mentored by example and allowed me to make mistakes, knowing that it is always valuable to learn from one’s mistakes. He provided me many opportunities to interact with the California fruit industries taking me along on technical visits and helping to set up cooling tests and observe him and Gene design experiments, discuss their results and how to interpret these. As I neared the end of my time as a graduate student he made sure that I gained experience in giving talks to large groups even though I may have lacked the self-confidence to do so… he always told me that everyone needs a little practice. He did not have to do these things, but he did because he saw the value in teaching by example and experience.
I know he gave this special treatment to all his graduate students. Adriana Dinamarca Rushing, a former graduate student in the mid 1980’s wrote this to me last week:
"If I can say something in a few words as a former graduate student, I was so fortunate to have Gordon as a Major Professor. He cared so much about the industry, teaching and especially all the students or anyone who will come to his office to ask a simple or more elaborated question. He was always very friendly, down to earth, honest, helpful and knowledgeable. He also was like the "father figure" to most of us foreign students. You could see the goodness in everything he did and that he was a role model professionally and personally."
The contributions that he made first as a scientist and extension specialist but more importantly as a human being are remarkable. His impact is being felt around the world by improved fruit handling practices and by the actions of those so fortunate as to have worked and learned from him.
Mary Lu Arpaia
March 2012
Gordon Mitchell and Carlos Crisosto at the F. Gordon Mitchell Post Harvest Lab located at the UC Kearney Agricultural Center
Making a Difference: Produce Handling in Developing Economies
There is a wide schism between the sleek mechanical harvesting machines that briskly traverse California’s fertile croplands versus the field worker with a machete and head-basket, or possibly a donkey laden with woven baskets, that is still most commonly found in many nations.
Produce loss continues to be a significant problem. Worldwide, it is estimated that as much as one-third of the produce grown is never consumed by humans (Kader, 2005). Many logistical challenges contribute to this loss, including: ineffective or absent cooling systems, slow and rough transportation, physical damage from rough handling, and poor sanitation conditions.
In 2010, one of the most popular free titles available on the Postharvest Technology Center’s web site was “Small-Scale Postharvest Handling Practices: A Manual for Horticultural Crops”. Written by Lisa Kitinoja and Adel Kader, and currently translated into 10 languages, this title was downloaded by over 22,000 readers last year. While this useful resource is very popular in the United States among small-scale farmers, over 8,000 readers benefitted from the useful content translated into Indonesian, 4,000 from the Vietnamese translation, and over 3,000 from the Arabic translation. Readers learned information about the curing of tuber crops, designing picking poles and catching sacks to gently harvest fruit, and efficient designs for packinghouse layout. (View all ten translations under the section on “Small-Scale Postharvest Practices” at: http://postharvest.ucdavis.edu/Pubs/publications.shtml.)
“Many simple practices have successfully been used to reduce losses and maintain produce quality of horticultural crops in various parts of the world for many years,” asserted Lisa Kitinoja of Extension Systems International. “You don’t necessarily need costly handling machinery and high-tech postharvest treatments to be able to deliver quality produce to the marketplace. However, effective management during the postharvest period is key to reaching the desired objective.”
While most California produce shoppers are grateful for the quality and variety available in our markets, it’s nice to know that an effort is being made to improve the produce available to others not quite as fortunate as we.
Photo: Kumasi Retail Produce Market, courtesy of Adel Kader.