Ocean Heat Dome Steams Coastal China: Shanghai to Near Very Dangerous 35 Degree Celsius Wet Bulb Temperatures This Week

Shanghai Under Ocean Heat Dome

Shanghai, southeast China swelter under Ocean Heat Dome.

(Image source: NASA/Lance-Modis)

An ocean heat dome that formed over a broad area of the Pacific Ocean, the South and East China seas, and a large stretch of coastal China during late July continues to create a dangerous combination of record hot temperatures and high humidity.

According to reports from AccuWeather, the sweltering coastal China town of Shanghai hit a new all-time record high temperature of 105.8 degrees Fahrenheit (41 degrees C) on Tuesday. But this marker may just be a milepost to what is predicted to be a 107-108 degree scorcher on Wednesday and Friday. With humidity predicted to be around 50% and barometric pressure readings expected to hit 1005 millibars, these represent extraordinarily dangerous conditions.

The human wet bulb limit: 35 C

Recent climate papers by former NASA scientist James Hansen have issued warnings of the potential for wet bulb temperatures on the surface of the Earth to start to exceed levels that are lethal for humans at 35 degrees C  for longer and longer periods as humans continue to warm the atmosphere. Hansen notes:

One implication is that if we should “succeed” in digging up and burning all fossil fuels, some parts of the planet would become literally uninhabitable, with some time in the year having wet bulb temperature exceeding 35°C. At such temperatures, for reasons of physiology and physics, humans cannot survive, because even under ideal conditions of rest and ventilation, it is physically impossible for the environment to carry away the 100 W of metabolic heat that a human body gene rates when it is at rest.

Different from direct air temperature, wet bulb readings measure what air feels like on the surface of the skin. The measure simulates the cooling effect caused by human sweat evaporating from the skin surface. In very dry, hot conditions, human skin temperature can remain below this lethal level as the rate of evaporation increases due to dryness. Since most of the world’s hottest regions are very dry, humans can withstand air temperatures of 120 degrees (Fahrenheit) and above. Thankfully, it is very rare that extraordinarily hot and humid conditions occur in the same locations. This is generally due to a cooling affect provided by an adjacent ocean mass — as most damp regions are also near or surrounded by cooler ocean air.

The Ocean Heat Dome

Enter the weather conditions forecast for Shanghai tomorrow and Friday…

A massive heat dome high pressure system has settled, not just over land areas of China, but directly over a large region of the Pacific Ocean and adjacent China seas. The result is that sea surface temperatures are now ranging 1-4 degrees Celsius above the already warm 1971-2000 average with a large area showing temperatures above 30 degrees Celsius (86 Fahrenheit). This large region of hot water and corresponding hot ocean air is pumping both heat and humidity into the Shanghai region. Hot ocean air is being pumped over Southeast Asia where it mixes with the already baking land mass air to form a brutal brew of very high heat and high humidity. The clockwise flow of the heat dome then pulls this mixture of record hot and humid air over the highly populated regions of Shanghai.

These ocean-based heat dome conditions are not normal, with typical heat dome conditions usually forming over land. The danger in this particular set of conditions is that very high heat combines with higher than usual humidity to result in much greater heat injury risks for humans.

Ocean heat dome

Sea surface temperatures under Ocean Heat Dome

(Image source: Weather Online)

Forecasts for tomorrow and Friday are showing Shanghai temperatures will probably reach at least 107-108 degrees Fahrenheit (42 C) in an area where relative humidity is forecast to be 50% and where barometric pressures are forecast to remain around 1005 millibars of mercury. This brings us to the extraordinarily dangerous high wet bulb temperature of 33 degrees Celsius.

Please do your best to stay safe

In such instances, the best defense is to find a cool, shaded location and limit exposure to heat during the hottest times of the day. Drinking cold fluids can also aid in reducing core body temperatures. A common heat mitigation aid is freezing a bottle of water and carrying it in a pocket next to your thigh. The cold bottle will contact the skin near the femoral artery, cooling blood there and transporting this cooler blood throughout the body. If extreme heat is still too much, placing the bottle in direct contact with the large veins in the neck will provide even more efficient cooling. This simple cooling pack also doubles as a means to replenish vital fluids.

Under such conditions, it is also important to be alert for signs of heat exhaustion and heat stroke to include:

  • Confusion
  • Dark-colored urine (a sign of dehydration)
  • Dizziness
  • Profuse sweating
  • Weakness
  • Muscle cramps
  • A lack of sweating

China has also activated emergency operations facilities and is providing information and aid in the hardest hit regions.

Unfortunately, record heat is expected to continue over Shanghai through at least next Wednesday with only one day expected to see below 100 degree (F) readings. With so many already dealing with heat stress, our best hopes are that all there will have the means to remain safe.

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Worst Heatwave in 140 Years Turns Deadly After Scorching China for More than a Month; Forecast Predicts No Relief

Heatwaves — they’re a regular risk of summer. But this year has seen a rash of particularly vicious and anomalous instances. As the Arctic baked under numerous heatwaves in which temperatures shattered the 90 degree (Fahrenheit) mark, as the US experienced some of its worst southwestern heat ever recorded, as the UK experienced record summer heat and wildfires, and as Spain sweltered as temperatures soared above 40 degrees C (above 104 F), China was experiencing its own version of a global warming amplified scorcher.

The worst heatwave in 140 years smothered about 1/3 of China, a sprawling area covering about 3 million square miles. At the heat epicenter, Shanghai, a region inhabited by 23 million people, saw daytime temperatures above 35 degrees C (95 F) for more than 25 days during July of 2013. On July 26th, Shanghai experienced an all-time record high of 106 degrees Fahrenheit (42 C), a level not reached since record keeping began in 1873.

Shanghai also reported ten deaths and far more numerous heat injuries for the month, as the hot weather intensified this Wednesday, while dozens of deaths have been reported over a large, scorched area of south-coastal China.

Throughout this week, China has been issuing its second highest national heat alert. This level requires the establishment of a 24 hour emergency operations center in order to provide emergency response and support capabilities for the hardest hit areas. The highest alert level is so extreme that China has never used it. Unfortunately, as the human-caused warming trend continues, it seems ever more likely that such a high heat category will have to be put in use.

Those living in Hangzhou, a region located about 100 miles to the southwest of Shanghai, may have already thought officials should have used such a marker as temperatures soared to above 104 degrees Fahrenheit (40 degrees C), for six out of seven days over the past week. Meanwhile, Xiaoshan saw a new all-time record high temperature of 108 degrees Fahrenheit (42.2 degrees C) on Tuesday. The coastal city of Ningbo saw temperatures hit 109 degrees F on July 26th, the highest temperature ever recorded for a coastal city in all of South-East Asia.

In what has become a kind of macabre ritual in widening areas of the world affected by extreme heat, Chinese residents laid out shrimp and eggs to fry over scorching road surfaces. More ominously, the extreme heat threatened crops even as it baked rivers and lakes setting off massive fish kills from heat and anoxia. In some regions, the fish kills were so extreme that an estimated 60 percent of all fish were lost (normal summer heat may result in 5-10 percent fish losses in affected regions).

In order to protect crops and fish, China has engaged in a cloud seeding effort in hopes of spurring rainfall over scorched areas while it is urging localities and fish farmers to pump new water into ponds and rivers to enhance oxygen levels and reduce fish losses.

Heat dome, coastal flow, very high wet bulb temperatures

Coastal region of China hardest hit by heat wave.

Coastal region of China hardest hit by heat wave.

(Image source: Lance-Modis)

A dome of hot, moist air has persisted over this region for nearly a month now. Though rainfall and even flooding events have occurred due to a flow of Pacific moisture over the area and the occasional onrush of tropical cyclones, these rainfall events have done little to alleviate a combination of oppressive heat and humidity.

Flows off the ocean would normally help to somewhat alleviate the heat, but an area of typically hot summer water is now showing readings 1-2 degrees Celsius above average. This broad region of hotter than normal surface ocean waters off China now show temperatures higher than 30 degrees Celsius (86 degrees Fahrenheit). Windflows issuing off these extraordinarily hot ocean surface areas are not very helpful in cooling the baking land. Worse still, the heat dome conditions — stifling airflow, concentrating heat and locking in place a layer of heat amplifying haze and smog — have persisted for much of the past month. This combination of less effective ocean cooling and heat dome conditions has resulted in a terribly severe heatwave for this coastal region.

Coastal heatwaves are particularly oppressive and potentially lethal due to the fact that humidity tends to remain higher than in more arid regions. A wet bulb temperature above 35 degrees Celsius (95 Fahrenheit) is considered lethal for human beings. Those living in Southeast Asia are well used to living under sweltering conditions of high heat and humidity. But as temperatures approach this human threshold (25 C + wet bulb temperature), even those acclimated are at increased risk. So both extreme heat and high humidity likely contributed to the sad and tragic dozens of instances in which lives were lost during this particular event.

The forecast for Shanghai next week calls for continuing record heatwave conditions with high temperatures ranging from 99 to 102 degrees (Fahrenheit) from Sunday through Saturday. With humidity levels near 50% this means wet bulb temperatures will approach 29-30 degrees Celsius during the hottest portions of the day. This continuation of a scorching summer heat wave will result in high risk of both heat injury and loss of life for those living in this sweltering region. With little to no relief in the forecast, this section of China is likely to remain under the fire of human-caused heating as August advances.

Links:

People Crops and Fish Suffer in China’s Heat Wave

Dozens of Deaths Blamed on China’s Heat Wave

Heat Wave Blamed for Huge Pile of Dead Fish

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