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ORG“Taishan Little Donkey” painstakingly tested many temperature variation data points in Winter Xiaowutai; “No Land Farmer” combined his own personal experience to vividly illustrate how cold waves and updrafts can create terrifying microclimates in localized areas. It clarifies an important point: the cooling coefficient — geography textbooks tell us that for every1000mincrease in altitude,6the temperature drops by one degree Celsius (hereinafter referred to as “degree”). This conclusion is sometimes drastically wrong!
According to observations by “Taishan Little Donkey,” during the arrival of a cold wave, the temperature can drop by1000mfor every9-12, with this value related to the intensity of the cold wave.
If on the day of the Lingshan incident, at an altitude of1050, Kongjian Village recorded-22degrees, then based on his measured data of a1000mdrop per11resulting in a-35.7degree decrease, the mountaintop would be-37~-38degrees, with the coldest period reaching approximately
Although the following mostly discusses the climate of Xiaowutai, the principles also apply to surrounding high-altitude mountainous areas at around2000meters..
Let me recall the unique harsh winter weather phenomena in the high mountains of Beijing’s suburbs.
Author: “Taishan Little Donkey”
1:“Mountain-Crashing Blizzard”:
Actually, cold air is not completely dry; it still contains a certain amount of moisture, especially cold air from the west. In the plains, due to weak convergence and lifting capacity, it generally does not cause snowfall. Snowfall in Beijing requires a collision between cold and warm air masses to form a front. But high mountains don’t need the cooperation of warm, moist airflows — their natural lifting advantage creates a “terrain front,” thus enabling snowfall. The strongest lifting capacity is found at Xiaowutai, where it can snow heavily for two days and nights on the mountaintop, while towns and villages at the foot such as Taohua and Changning see not even a single flake. Due to the strong winds accompanying the cold wave, this kind of snowfall takes the form of a blizzard.
2: Strong Updrafts
When a cold wave arrives, the pressure difference and temperature difference between the windward and leeward sides of the mountain are very large, resulting in strong updrafts, sometimes with wind forces exceeding10on the Beaufort scale. It can make people feel “weightless,” meaning that even when heavily equipped, standing on the “Enchanting Big Slope,” just a slight lift of the foot can easily raise you upward. Both I and Green Field netizen “No Land Farmer” have deeply experienced this. The danger of such strong updrafts is that they may prevent people from descending the mountain — perhaps the friends who perished on Lingshan were unable to descend because of this. Of course, strong updrafts can also lead to more intense blizzards. (Editor11In spring, after reaching the summit of Xiaohaituo and camping at the saddle, the fierce wind made it impossible to stand still. Just descending the gentle slope of the saddle took half a day, and using trekking poles with four-point support was necessary to avoid falling over)
[“No Land Farmer”: The ‘weightlessness’ caused by updrafts may seem fun, but it’s actually terrifying, because it’s2010On Labor Day that year on the tea mountain, as we were heavily laden and ascending an open grassy slope without tree cover, we encountered a strong updraft blowing from behind. The team struggling up Dongling Mountain also faced such winds—Flying Bird said the wind behind them was pushing them forward, but we felt as if the powerful updraft was lifting us bodily off the ground. At the time, my sensation was that my body had lost its center of gravity, and I (80weighing+just under20kilograms with my backpack) could only move upward effortlessly, completely unable to step back or turn around. Not far away, a lighter hiker with a rain cover on their backpack was lifted clean off the ground by the fierce gusts. Luckily, it was just a momentary blast; we dashed to the leeward side of the ridge while the wind briefly eased...
Looking back, the updraft we encountered seemed to come without warning. Meanwhile, the hikers on Dongling had been walking in the wind for some time, and it’s likely the wind grew stronger the higher they went. At that point, one should have considered how to counter such persistent, powerful updrafts during the descent—otherwise, getting down might have been nearly impossible...
On another occasion, during a winter climb of Xita, I mistook the flag clouds at the summit for terrain-induced winds (some sections of Xita’s ridgeline do have consistent side winds caused by the terrain) and recklessly charged into a fierce crosswind. The result, naturally, was getting blown over again while heavily laden—this time, toward the valley. Fortunately, I managed to stop the slide after just one meter. Later analysis suggested it was likely a whirlwind forming at the summit, and we had only encountered one side of it. Had we proceeded to the top, we would have faced the most intense “ascending immortal wind” (nearly10-level updraft).
This rant serves two purposes: first, self-criticism, and second, a warning to fellow hikers. Especially when climbing in winter, pay more attention to wind direction, cloud formations, and other weather signs, judge your situation rationally, and don’t act rashly. ]
3: Extremely high cooling rate
What our geography textbooks tell us—that temperature drops1000mper6degree—is sometimes wildly inaccurate. Based on my observations, during cold fronts, the temperature can drop1000mby9-12degrees, and this figure is related to the intensity of the cold front. If, on the day of the Ling Mountain incident, the temperature in Kongjian Village at an altitude of1050was-22degrees, then according to my measured data of a1000m-degree drop per11, the summit temperature would be-35.7degrees, and at its coldest, almost-37~-38degrees. I’ve previously shared a method for calculating mountain temperatures (Editor’s note: see below).
4: Sudden blizzards
“Farmers without land”: Sometimes, mountain blizzards can arrive even faster than summer thunderstorms. Last year on12May22, I experienced this on Xiao Wutai. The conditions changed from mostly cloudy with3-4-level winds to7-8-level winds and full blizzard conditions in roughly3minutes. I still haven’t figured out why this phenomenon occurs.
I thought at the time it was due to the clouds pressing down from the mountaintop, but Little Donkey disagreed.
At that time we were1750ascending, and when we looked up we saw dark clouds descending from the mountaintop, already spreading to2000meters above sea level. Based on this, I believed the snowstorm an hour later was caused by this.
“Little Donkey of Mount Tai”: If there's subsidence, the air warms up and reduces humidity, which hinders snowfall. But at that time, the snow suddenly intensified.
5: Inversion layer freezing rain
2010Year3Month14Day, “TTeacher”, “Jane” and others encountered moderate rain on Xiao Wutai1700initially, while at that time, the villages below the mountain and the mountaintop were both experiencing blizzards. The danger of inversion rainfall is that if unprepared, one can easily get soaked and then suffer from hypothermia.
(Editor’s note: An inversion layer, also known as the stratosphere (stratosphere), or the isothermal layertemperature inversion layer, generally speaking, in the lower atmosphere, temperature decreases as altitude increases. But sometimes in certain layers, the opposite may occur—temperature increases with altitude—and this phenomenon is called a temperature inversion. The atmospheric layer where a temperature inversion occurs is called an inversion layer.)
Personal experience with an inversion layer:We camped1750in a small saddle, and around midnight there was moderate rain. After breaking camp and descending about100meters, we encountered snowfall, and there were no signs of rainfall on the ground or trees, so we judged that it had been snowing continuously since midnight. This situation of snowfall at low altitudes while rainfall occurred at mid-altitudes puzzled us. Later, Little Donkey gave a very detailed explanation, but I didn’t remember it all—it probably had to do with terrain and wind direction. The moderate rain happened at midnight, which was actually fortunate for us, as everyone stayed in their tents, taking shelter from the rain and having breakfast. By around10a.m. when we broke camp, the rain had gradually lessened. If you get wet during a hike and then encounter heavy snow in the valley, the consequences can be severe. Because our shuttle vehicle couldn’t climb the icy slope, we had to trek two to three hours through the snow to meet the car.
By the time we reached the plains, the entire mountain was already completely shrouded in heavy snow, making it impossible to assess the conditions.
Winter on Xiao Wutai is the most climatically complex route around Beijing—you can encounter all sorts of conditions in the mountains. Therefore, having as complete gear and supplies as possible, as well as as conservative a plan as possible, seems to be the only choice for someone like me who lacks experience and knowledge. Of course, the knowledge and guidance Little Donkey continuously shares with everyone gives us direction on our mountain treks—at least I’ve learned and heard a lot on-site. As for how to judge and adapt in the moment, that requires combining theory with repeated real-world experience.
Regarding the low temperatures in Xiao Wutai in winter
I’ll briefly introduce it based on an experiment conducted on New Year’s Day one year.
One: The situation on New Year’s Day
On New Year’s Day, the worst conditions on Xiao Wutai occurred on the morning of the2and the night of the-3. On the morning of the 2nd, as cold air arrived, the temperature dropped sharply. The daytime high temperature at the top of North Platform fell from-21degrees at 8 a.m. all the way down to3The early hours of the night of the 90th-34degree. We3When we broke camp on the morning of the 92nd, the temperature was still dropping. We estimated3that the highest daytime temperature on the 93rd would be only around-27degrees, and by the evening it should have dropped to around-35degrees.
As it turned out, fortunately the friends from Green Field were well-prepared, but some still suffered minor frostbite.
Second: Historical Low Temperature Estimates
How cold can it get at Xiaowutai?-40Minus what?? Very easily — according to historical data, the extreme minimum temperature at Xiaowutai is estimated to be around-48minus [number], or even-50[lower number], likely occurring in1972[year]. Some may ask: But wasn’t that in the distant past? Now with global warming, do we need to worry about it? Wrong.08 In the years09,10, and-42° and-45°. So we must not let our guard down.
Third: A Simple Calculation of Xiaowutai Summit Temperatures
In winter, Xiaowutai isn't always ragingly cold. In fact, when there's no cold advection (strong winds causing temperature drops), the temperatures are quite tolerable, even comfortable. This is because cold air is denser, and without upward air currents to hold it at the summit, it quickly sinks. At such times, the temperature difference between the foothills and the summit isn’t much.
But once cold air arrives in North China, the strong northwest winds are influenced by the terrain and continuously force the air to rise forcefully toward the summit. According to the principle of adiabatic expansion and cooling as gases rise, the temperature at the summit becomes very low. This involves both dry adiabatic and moist adiabatic processes. Simply put, the dry adiabatic process refers to rising air that doesn't form clouds or precipitation, while the moist adiabatic process involves precipitation forming at a certain altitude on the mountain. In the dry adiabatic process, the temperature drops by100mdegrees for every1meters of ascent, while in the moist adiabatic process, due to heat release from condensation, the temperature drops by100mmeters.0.6degrees for every
Taking the cold air mass around New Year’s Day as an example, snowfall likely occurred around2500(based on observation). The temperature at the foothills was-16degrees (at Taohua, elevation1000). Then, as one ascends from1000mto2500m, the temperature dropped15degrees, from2500-2840(North Platform), the temperature dropped again3.4X0.6=2.04. At this point, the summit temperature was-16-(15+2.04)=-33.03.The actual measured value was exactly-34degrees (explained in my hiking forum post), where theory matched practice.
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Four: Analysis of several extreme low temperatures (-40and below) in the past four years
Based on meteorological data, I’ll analyze a few super low temperatures in the past4years
I remember that day in Beijing, the daytime high didn’t exceed-9degrees, with howling winds. What about Xiao Wu?12In21, the daytime high on Xiao Wu was-38, the nighttime low-43, accompanied by11level strong winds.Absolutely hellish
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This time on Xiao Wu Platform, the daytime high was-36, the nighttime-41, with winds at10-11level
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Let’s look at previous temperatures to assess the severity of this cold wave.21On the day at the foot of the mountain, the daytime temperature was6-7degrees
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2010New Year’s Day cold wave
This one is still fresh in everyone’s memory — Beijing experienced its heaviest snowfall in recent years, Haidian1In5The lowest temperature was recorded in the early hours of-20.2, breaking historical meteorological records in many parts of North China.
What about Xiaowutai? The minimum is hard to calculate, but-40degrees were easily shattered, and the maximum temperature should have been-37or so.
Did everyone see the altitude at the foot of Xiaowutai—950 metersin the Changning Township area—-32recorded-52…? The probability is very low, and I’ll explain why.
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2011In the year1, in the month of15, a strong cold front
—this didn’t meet the criteria for a cold wave, but2010-2011it caused the extreme low temperatures in major cities this winter, including-11.6in Beijing’s southern suburbs,-11.6in Jinan,-9.4and in Nanjing.
I also went to Xiaowutai this time, but unfortunately, due to time constraints and thermometer issues, I only managed to record a few data points:1On the night of14, at an altitude of1200at the foot of the mountain, it was-22degrees,1500at the campsite it was-25degrees.
Calculating from that, the summit of Xiaowutai would have been right around-40, with daytime lows of around-29to-30, and wind force of about6-8on the Beaufort scale.
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Appendix: Reasons for Low Temperatures in Winter
The occurrence of very low temperatures in winter mainly involves3several scenarios:
1: When a powerful cold air mass reaches the level of a cold wave or even a strong cold wave, no matter how high the temperature was beforehand, it can produce astonishingly low temperatures afterward—for example, the cold waves in08year12month21and09year1month23.
2, or when cold air is accompanied by post-snowfall radiative cooling, such as the New Year's Day cold wave in10.
3: After multiple consecutive cold air masses have created a foundation of low temperatures earlier on, even a moderately strong cold air mass can result in relatively low temperatures—for instance, the case in2011year1month15. And if1,2,3all come together… well, that’s obviously a once-in-a-century cold wave. The New Year's Day cold wave in2010was a classic example, but the conditions1were a bit weaker, otherwise…
One subtle difference:
Those who carefully observe weather forecasts and actual conditions may notice: when there is strong wind, the minimum temperature is often not as low as the temperature on the following windless day—this is even more obvious after snowfall. Strange? The principle is that the cooling process includes both the transport of cold air and radiative heat loss from the ground. Clear skies, snow cover, and calm winds all favor radiative cooling. At the end of a cold wave, although the strong winds have stopped, the cold air has already arrived, and the radiative capacity at night increases. On this basis, further radiative cooling will definitely lead to even lower temperatures.
So1month5, the situation in Weining, based on experience, must have been due to wind cessation and radiative cooling from snow cover. At that time, without any lifting effect, it was hard to affect the peak of Xiaowu Mountain.-32Based on experience, it must be due to the snow radiation after the wind has died down. At this time, without any lifting effect, it’s hard to influence the summit of Xiaowutai Mountain.
How to distinguish between cold advection low temperatures and radiative low temperatures based on weather forecasts
There is a simple method: if on a certain day the difference between the daytime maximum temperature and the minimum temperature is very small, and there is4-6A northwest wind of force 8 generally indicates cold advection at low temperatures. Conversely, even lower temperatures are due to radiative cooling, which is not as severe.
1: When the Central Meteorological Observatory issues a yellow or even orange cold wave warning, it’s best not to go. What awaits you will definitely be-40extreme cold, accompanied by8gale-force winds of force 8 or above — that’s hell on earth.
2: During the depths of winter, avoid going even if there’s only a moderate to strong cold air mass in North China. Although the cold air isn’t particularly intense, the baseline temperatures during mid-winter are already very low, and once the airflow rises to the mountaintop, the temperature becomes extremely frigid.
3: If you really must go, make sure to prepare the necessary gear and ensure everything is foolproof — otherwise...
Due to various reasons, many experiments I designed were never carried out, so there’s still much to improve. For example, my judgment that the difference in radiative cooling between the summit and base of Xiaowutai Mountain is minimal is based solely on theory, without data support. Also, how strong does the cold air need to be to lift gases up to the summit of Xiaowutai and create such low temperatures? If the ascent speed is slow, the adiabatic model can’t be applied — how significant is heat conduction? ??? These require testing during weak cold air processes, but I haven’t done that yet. So there are quite a few gaps, and I look forward to everyone’s help.
Add Haituo Mountain.-30The data at the mountain base at this temperature — “Lean Meat” should remember it well. You can estimate the temperature difference coefficient at that time based on this table.
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(End of article)