Intro: The highest capital city
Bolivia is situated in the Southern Hemisphere on tropical latitudes, but it’s western part’s high elevation make the closure to the Equator no more than pure statistics. With around 3600 meters altitude in the center area, La Paz is the world’s most elevated capital city. Contrary to the usual setting, here the airport is situated well above the city itself, therefore at 4000 meters elevation the air in El Alto (spanish for “The Heights”) is even thinner. The explanation is the local topography: La Paz is sheltered in a deep canyon, below the wind-swept Altiplano (“High Plateau”) where the flatter terrain is more suitable for an airport.
If somebody came here from normal elevations he/ she certainly will feel some signs of the “mountain sickness” in just a couple of hours. This include headache, nausea, dizziness, tinglings in the limbs and shortness of breath. The last one is very obvious while doing some effort, like climbing the steeper streets of the city. As the urban agglomeration has a very complicated relief you have a lot of inclined terrain to deal with. Better take it easy in the first days. However, some people acclimatize much easier than others. It’s more a genetic thing than something related to physical fitness.
Another interesting fact regarding the local climate are the big daily thermal fluctuations. This is the most outstanding in the dry season, which here coincides with the (austral) winter months. From June to August the temperature tipically fluctuates from near freezing in the night/ morning to 15-20 degrees Celsius in the early afternoon hours. But, because of the high UV radiation the daytime temperatures felt much warmer. A 17-18 degrees Celsius in the sun here on the Altiplano is more like a 25 degrees at sea level. Really sharp contrast between the sun and shade. The sky is normally clear or partially covered with higher clouds, the possibility for any kind of precipitation is pretty low in the winter months.
Despite the lack of oxygen the streets of La Paz and the neighbouring El Alto are very crowded. From food to clothes and car parts, everybody is selling something. The traffic can be incredibly slow, but the locals are very patient and peaceful. Conflicts between the citizens are rare. Tourism is one of the main income in this poor, landlocked south-american country, so you will see lots of backpackers wandering in the center area.
Choosing the target
Everybody heard about the expressions “lunar”, respectively “martian landscape”. It refers to a very dry and barren place, usually a desert, where no vegetation is present and the terrain is mostly made of by bare rocks and/ or clay. It is also known that because of the lack of an atmosphere the climate of the Moon and the Mars is very severe, fluctuating between extreme cold in the night and blistering heat in the daytime. This is mostly because of the lack of water vapour in the air, whose presence regulate/ moderate the heat transfer on Earth’s surface. However there are some places on our planet where the climatic conditions remind of these dead celestial bodies, presenting huge daily temperature fluctuations. Where are they and which parameters are responsible for the most extreme conditions on Earth?
First you need clear skies. Clouds are composed of water vapour, which keeps the heat trapped in the lower atmospheric layers. Deserts are known to have less cloudy days than any other ecosystems. Second you need high altitudes. The thinner the atmosphere, the less heat can be kept inside during the nights and more solar radiation will reach the surface during daytime. So high elevation deserts are better suited than the ones situated near sea level*. Thirdly you need high solar angle to have even greater differences between day and nightime conditions. It means high elevation tropical deserts are the best choice. And fourthly you need concave topography, because it heats more in the daytime (reradiation from the sides) and cools more in the night hours (collecting the denser, colder air like a bowl). The theory is ready, let’s check the practical availabilities.
How about the Altiplano? It is dry, it is very high, it is situated on tropical latitudes and there are many non-active volcanoes with well preserved, deep craters. All the four conditions matches. Reliable climatic statistics of the region are pretty scarse on the Internet. On wordclimate.com I’ve found La Quiaca weather station on the Argentina-Bolivia border (around 3400 meters elevation) to have the biggest average daily amplitude. Here in June and July the temperature fluctuates between -7 and +15 degrees. Regarding the precipitations the western part of the high plateau is even drier, so I suppose the thermal amplitudes can be even greater in the region situated around the triple border between Argentina, Bolivia and Chile, known as “Puna de Atacama”.
One of the biggest astronomical observatories in the world have been built on the chilean side of the Atacama Plateau. Why? Because the region offers one of the clearest skies on Earth, year round. It is said the air here has comparable transparence with the one above the South Pole. After studying the local conditions from the weather statistics of the ALMA observatory I’ve concluded the biggest drawback of the regions climate is the wind. Air movements are mixing the layers, destroying the forming inversions in the nightime and cooling the ground in the daytime. Beside its dryness, the winter is also pretty windy on the Altiplano. So, apart from the already mentioned four, I will need also a fifth parameter: Luck.
But where exactly can be the place with the highest daily thermal amplitude? After stopping at Juriques volcano on the Chile-Bolivia border, finally I decided to choose a lesser known crater situated a little more to the north on the bolivian side. The mountain is named “Aguita Brava”. The location is marked only on good topographical maps. The barren volcano is close to 5500 meters high with a crater of around 800 meters wide and 80 meters deep. The bottom of the caldera is situated at 5320 meters elevation. Because this mountain has a somewhat less prominent topography than Juriques, which rises abruptly above the Atacama desert with little protection from the dominant, westerly winds, I presume Aguita Brava crater has better chances to produce good night-time inversions. The caldera itself is also a little more sheltered inside the volcano, with slightly lower, but still enough good sky view factor (around 0.91-0.92, according to my calculations on Google Earth).
Winter is the dry season here, it means more clear skies and greater chances to have huge daily amplitudes. Even if rare, but snowfall is possible during the colder months too. In the frigid and bone-dry conditions the snow doesn’t melt, but sublimates (transforms directly from the solid to the gas phase). Under the strong sun the white blanket wanishes rapidly, however the wind collects the snow in the sheltered areas, often blocking parts of the roads on the high plateau. Timing: second part of June.
Access to the volcano: There are only a few roads in this remote area and none of them is paved. Despite the place is almost uninhabited I found out there are some touristic circuits, which approaches my target pretty well. Around 10 km’s to the north of the crater is an attraction composed of many small geysers named “Sol de Manana”. This place is situated close to the highest part of the Uyuni-San Pedro de Atacama (Bolivia-Chile) road, and when the conditions permits (no snow blockages) has daily visitors year round. The geysers are situated above 4800 meters elevation, only 600-700 meters below my chosen mountain. Properly acclimated this means a one day hike, though with a heavy backpack can probably be quite exhausting.
Aguita Brava is situated inside the Eduardo Avaroa Andean Fauna National Reserve, a protected area with many bird species, including flamingoes. These can survive in the harsh conditions thanks to the salt lakes like the reddish Laguna Colorada, where they eat the alges. Laguna Verde is another local attraction, but this lake supports no life, because of the arsenic content. The green color is given by the copper minerals and is more intense during windy weather. Licancabur volcano rises above the surreal lake, where the highest level of UV radiation on Earth (43.3) has been measured. Though this was registered during the summer, because of the tropical latitudes the sun has a pretty high angle even during midwinter and the clear skies – thin atmosphere combination gives a solid recipe for sunburn if unprotected.
*The rumour about the Sahara to have freezing temperatures during the nights and up to 50 degrees in the daytime during a single day is a very prevalent false myth on the net and school books too, actually probably a misunderstanding. The truth is in the winter nights the temperature can go sometimes below 0 degrees and in the hottest summer afternoons can approach 50 degrees. But when there is freezing in the night, the daytime highs will probably reach around 20 degrees and when the afternoon heat is close to 50 degrees, it is unlikely to cool down below 20-25 degrees in the following night.
Brief summary of the research
My plane landed in El Alto on June 16 in the morning. I spent only 2 days in La Paz before taking the domestic flight to Uyuni. Because of a recent snowfall in the high Andes the usual touristic circuits were not fully open and the approach to the geysers area in the next days (my starting point) was questioned. The company that I contacted from home gave me a private driver to take me nearby the fumaroles in a single day. Though the road was partially snow covered in the last quarter, but we managed to get very close to Sol de Manana without any problems.
From this place (4850 meters elevation) I left the car and started the slow hike up the mountain (10-12 km farther to the south). I set up my camp in the afternoon on the volcanic plateau slightly below 5000 meters altitude. No tent, only bivy sack + sleeping bag, sheltered behind a boulder. I was battling mountain sickness, but the weather conditions were very good (clear skies and no wind) during the night. Feeling better I climbed the mountain in the dark. Before the sun reached the bottom of the caldera I was there and soon the mini weather station started his activity (June 20, before 8:30 AM). The coordinates of the study area are: 22.30.762′ S, 67.47.744′ W, the altitude is around 5320 meters.
The logger’s sensor was set inside the helical radiation shield (donated by Barani Design Technologies) around 170 cm height, mounted on the top of a photo camera tripod. The logger itself was packed in a plastic bag and sheltered under the snow to protect it from the extreme cold in the night. The device recorded a temperature value every 5 minutes from the time it was started. I left there also an alcohol minimum thermometer to measure the lowest temperature of the entire research period (mostly for the case if the logger will have some trouble). A precision electronic device was used for instant measurements.
I collected the equipment 7 days later (June 27, around 1 PM), when unfortunately I found the tripod with the devices fallen over and partially buried under the snow.
During the research period the sky was generally clear or partially covered by higher clouds, but some of the days were very windy. The first day was my lucky strike, when I had perfect conditions for strong inversions and extreme daily amplitudes. After the second day the weather became more unstable (but without new snowfall) and (concluding from the logger’s graph) probably during the following night the tripod fell down. On 27 at midday when I collected the equipment it was strong gale on the crater’s rim and surprisingly even at the bottom.
The caldera was partially covered by snow during both visits, the ratio between the covered and uncovered parts was around fifty-fifty. The snow below the tripod was 20-25 cm deep, but just a few meters farther it was completely missing.
The lowest temperature registered by the logger during the one week research period was -26.6 degrees Celsius, the highest (reliable) +4 degrees Celsius, giving also the biggest daily thermal
amplitude : 30.6 degrees. Close to the snow surface I recorded -34.3 degrees with the precision electronic device (instant measurement) and below -35 with the alcohol minimum thermometer.
I spent 3 nights on the mountain, two nights on the first research trip (same camp between the geysers and the peak twice) and one night on the last one (on the other side of the crater at similar 5000 meters elevation on the volcanic plateau), visiting the caldera only two times (first in the morning of June 20 and finally in the early afternoon of June 27). The days between I spent in a hostel in Uyuni settlement and on the other side of the Salar de Uyuni, around 250-300 km’s to the north.
There are no settlements in the area, only a mine some km’s farther on the road from the geysers. The crater is completely lifeless, but the highest plants (small yellow patches) can reach around 5200 meters elevation on the slopes of the volcano. I’ve also spotted some seagull-like birds above my camp and vicunas not far from the fumaroles.
The instruments used in the field
-One LogTag Tred30-7R data logger with the measuring range between -40 and +99 degrees Celsius, 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 helical solar radiation shield from Barani Design Technologies: https://www.baranidesign.com/
To be continued…