Intro: The coldest capital city
Mongolia is well known as one of the coldest countries in the world and his capital city, Ulaanbaatar is undoubtedly the coldest one. With a January average below -20 degrees Celsius and occasionaly reaching below -40, this place is not for the weaklings. Beside the severe climate the city is enshrouded in heavy smog, making the breathing even more difficult. The pollution is caused by the phenomenon known as “thermal inversion”, when the dense cold air of the wintertime is sinking to the bottom of the valleys and basins keeping the smoke and other dry particles in the lowest atmospheric layers. The smog is the strongest in the late night and early morning hours when the cooling is the most intensive. This can cause many problems including road accidents and flight delays. Because of these complications there are plans to move soon the capital’s airport to a new place that is more than 50 km’s from the city. The actual “Chinggis Khaan” (named after the founder of the Mongolian Empire) airport is situated about 15 km’s from the center and because of its location in a flatter and more open area is even colder than Ulaanbaatar itself. The temperature difference between the two on an average winter morning is around 5-6 degrees Celsius. In the day of my arrival it was a “mild” -25. But we aren’t there yet.
Choosing the target
I have a big passion for deserts. But also for the cold. How about the coldest desert? I’ll try to found it.
With an annual average below -50 degrees Celsius and reaching below -80 degrees in the toughest winter days, the interior of Antarctica is unequivocally the coldest place on Earth. It can be considered a desert if your classification is based only on the precipitation ammount which is extremely low there. But if your criterions are more complex and it includes also the landscape component, then you must switch your search to the Northern Hemisphere. Yakutia in Eastern Siberia is the coldest region in the boreal half (also has the coldest permanently inhabited places), but there is only taiga and tundra zone, no deserts. That’s why most sources come up with the Gobi as that one is the biggest and most known example of what a cold desert is. But it’s not the coldest one. The Gobi is situated in the southernmost part of Mongolia (also continues more to the south in neighboring China) but there are some smaller deserts in the north-western part of the country where the winter averages are much lower than in the famous stony desert.
The mean January temperatures in the mongolian Gobi are mainly between -12 and -20 degrees Celsius (Dalanzadgad -15, Sainshand -18 degrees) and in the chinese part mostly between -8 and -15 degrees (Dunhuang -8, Ejin Qi -11 degrees). Pretty low for sure, but not even close to the bone chilling -33 degrees of Ulaangom in Uvs aimag* (local administrative division, similar to province or county). The town is situated in the Uvs Lake’s basin, known as one of the coldest places in Central Asia, not far from the lesser-known Boorog Deliyn Els sandy desert. In this wasteland is a village named “Zuungobi”, which is the place where the lowest temperature in entire Mongolia was measured: -55.6 degrees Celsius. Yeah, that’s cold. And it’s a desert.
From October to April the land of Genghis Khan is affected by the Siberian Anticyclone, a huge collection of cold and dry air masses that is responsible for both the highest atmospheric pressures and the lowest temperatures in the Northern Hemisphere. Actually the center of the Siberian High in midwinter is in north-western Mongolia, consequently here was recorded the world’s highest barometric pressure. Most Internet sources are claiming that Tosontsengel of Zavkhan aimag holds the title with 1085.7 mb (millibars), but there is a place in the western part of the same aimag which (according to the statistics found on Ogimet) have reached even much higher values, like 1098.7 mb in the morning of 9 March 2016. This occured during an unusually strong cold snap when the small village experienced also the lowest temperature in the country for this month, a staggering -54 degrees Celsius. Tsetsen Uul, the peculiar settlement is located in a high altitude basin in the western part of the Khangai Mountains, not far from the limit of the sandy area, which extends here from the Great Lakes Basin, along the Hungui river and its (mainly former) tributaries. In some parts the sand dunes are reaching 2200-2400 metres in elevation, therefore it can be considered the highest desert in Mongolia. Because this region receives a little more rainfall and has cooler summer climate than the western, lower elevations, in some parts you can see pine trees between the sands. This high altitude sandy area raised my attention and I was starting to speculate if it can be the coldest place in the country, respectively the coldest desert in the world.
Because of the strong thermal inversion caused by the anticyclone, as a general rule, in the mongolian winters the lowest places are the coldest, therefore the Uvs Lake’s basin, which is one of the lowest places in the country (below 800 metres at the bottom), is also one of the coldest places. But the reality is a little more complex as Tosontsengel, Tsetsen Uul and Otgon settlements are all situated at much higher elevations (1700-2150 meters) and despite of this they can cool down to similar or often to even lower values than the formerly mentioned region. The explanation is that all three are situated in valley bottoms, which are collecting the sinking cold air from the nearby mountains. Actually the relative position what matters here, not the altitude itself. What’s more, if sufficiently flat and/ or enclosed, the highest basins can be the coldest ones, as in thinner air the nocturnal heat loss is more powerful. The Uvs Lake’s area is so cold because it’s a deep endorheic hollow, from where the collected cold air can’t escape in any direction. If the same topography could exist at higher elevations it could produce even lower temperatures.
In sandy areas, between the dunes are many enclosed, concave relief forms of different sizes, ranging from 1-2 to more than 50 meters deep. With the help of GoogleEarth I identified some huge hollows on the surface of the high elevation desert mentioned before. Subsequently I obtained a digital elevation model (DEM) of the area which also confirmed that some of these negative shapes are around 50-60 meters deep. The endorheic depth is the altitude difference between the bottom and the “outflow point” (the lowest elevation on the rim). The topographical aspect is exactly the same as in the case of the karstic depressions (dolines and uvalas) which are known to produce extremely low temperatures during clear and calm winter nights, therefore often referred to as “frost hollows”.
Between the deeper concavities noticed on the desertic plateau I picked out one, whose parameters (the combination of elevation and depth) appeared to be the most convenient for my research. The hollow has an endorheic depth of around 50 meters and it’s bottom is situated about 1960 meters above sea level. It has a roughly circular shape with a diameter around 1 km. According to my calculations the average slope of the depression is around 11 degrees. There is a term named “sky view factor” which consider the average slope as the major parameter responsible for the cooling potential of a given topographical place. Concave shapes are important for cooling because they are collecting the sinking cold air and also represents protection from the mixing effect of the wind, but if the slopes are too steep than the nocturnal heat loss will be significantly lessened by reradiation from the sides. Ideal is somewhere in between, mostly like a plate shape: concave but adequately open. By the way, eleven degrees is quite good.
The small negative shape appears on my detailed soviet miliary topographic map but without exact elevation data or a name for this particular place. The desert which encompasses also my target zone is named “Nariyn Golyn Els” (meaning “the sands of the Nariyn river”). No settlements and no roads are present in the immediate surroundings. The closest village is Erdenekhairkhan, situated to the south-west about 19 km in straight line. There is a dirt road which approaches more my target (about 10 km’s), reaching the southern limit of the dune field. I think that’s sufficiently close to can handle it by foot with a heavy backpack. GoogleEarth shows that the surface is sandy with some sparse vegetation (I guess shrubs), probably something like the Kalahari or the australian deserts, but the color of the dunes is lighter not reddish.
My small basin is part of the “Ulaagchiin Khar Nuur Bioreserve”, a protected area of high altitude sands, mountains and pristine lakes. Khar Lake, Mukhart river and Senjit Khad are the main eyemarks of the reserve, but I’m pretty sure that in the wintertime there are no touristic (if any) activities. We’ll see.
Brief summary of the research
I arrived in Mongolia in the morning of 15 January by the Budapest-Ulaanbaatar (through Moscow) international flight. From the mongolian capital I used domestic flight to Zavkhan aimag’s capital, Uliastai. At the airport a private driver was waiting for me, who was contacted by a tourism company from Ulaanbaatar. Previously this company supported me to obtain the visa at the mongolian consulate in Budapest and helped to arrange the transports and accomodations in the country during the entire journey. The private driver is a japanese 4wd car owner and takes me to his home in Erdenekhairkhan (around 110 km’s), which is the closest settlement to my targeted zone. From his village we approached the reseach area with the jeep, following a sandy and quite difficult track through the Nariyn Golin Els desert (around 20 km). We managed to get close to the target around 8 km’s in straight line. From this point I reached the chosen place alone by foot along the dune field, carrying the camping equipment and the meteorological devices in a backpack.
The area is remote, but still have some human activity in the wintertime. I saw 3 yurts and more herds of sheeps and goats along my hikes. Some horses and camels are grazing unsupervised on the dunes. The few people who are living here are moving on horseback and are doing daily circuits with their herds, the yurts are not moved in the cold season. Despite its isolation and severe climate, the desert’s surface was full with animal trails.
I raised my tent some hundreds of meters west from the actual research place, on the lowest part of the selected hollow’s rim, around 2007 meters above sea level. The tripod with the data logger inside the home-built radiation shield was set on the lowest portion of the frost hollow, about 1942 meters above sea level (according to the GPS). It means the depression’s endorheic depth is around 65 meters (16 meters deeper than according to GoogleEarth). The low-point’s exact coordinates are: 48.15.460′ N, 95.52.914′ E. The logger’s elevation above the surface was around 160 cm’s. This device was constantly registering the temperature from the afternoon of 17 January until the morning of 25 January. On the days when I was present in the region (three nights) I have set the minimum alcohol thermometer on the top of the radiation shield to measure the night’s lowest temperature. The precision electronic device was used to take instantaneous measurements of the air (holding the device in hand at head level while moving) and near the surface (leaving the instrument on the snow).
Outside a smaller exposed side from where the snow was partially missing, the depression was snow covered, with around 15 cm of snow at the bottom. The weather was constantly good, mostly clear or partially covered by cirrus and cirrostratus clouds, seldom with transitory altocumulus appearances. The wind was rare and mild, at the bottom mostly completely missing.
The research period was encompassing eight consecutive nights. From this I spent three nights in my tent, the remaining ones in my drivers yurt in Erdenekhairkhan.
The devices used in the field
-One Alpha TD80 data logger from Tempsen with the measuring range between -80, +70 degrees, an accuracy of +-0.5 degrees Celsius and a resolution of 0.1 degrees Celsius.
-One Greisinger GMH 2710-T digital precision thermometer with the measuring range between -199.9, +200 degrees Celsius, an accuracy of +-0.1 degrees Celsius and a resolution of 0.1 degrees Celsius.
-One meteorological alcohol minimum thermometer, USSR, 1988, with the measuring range between -50, +40 degrees Celsius (the first dash corresponds to -52.5 degrees).
-One photo camera tripod serving as the support for the instruments.
-One home-made radiation shield constituted of superimposed bowls made of polystyrene, covered with aluminum foil.
To be continued…