Interpretation of the logger’s graph (using LogTag Analyzer 3 software)

First day (June 21st)

It is the single day when I’ve spent significant time nearby the measuring equipment in the wadi. It was haze during my hike through the salt flats of Lake Assal before entering the gorge, with little wind. The logger started to record at 10:43 AM and the first reading can be considered legit as I waited sufficient time with the sensor placed under the helical shield to accomodate the ambience before pushing the start button. As I set the device for 2 minutes logging (short intervals) the curve has the typical “saw aspect” with many small ups and downs inside the general “big waves”. The temperature was rising more abruptly until 2:17 PM when reached 47.0 C, after which slowly increased until 3:59 PM when recorded the day’s maximum temperature of 47.4 degrees Celsius (quite normal evolution). During this time the sky was clear or partially covered, but the north-western clouds never managed to block the sun.

I left the area after 5:18 PM, when the temperature was already descending and the sun was reached by the clouds just a little before disappearing behind the walls of the valley. After spending some time outside the gorge where encountering a sandstorm after 6 PM I later returned to the tripod to see if it survived the strong wind (luckily yes). This interval coincides with a more abrupt drop of 2.3 degrees between 6:09 and 6:25 PM (from 46.3 to 44.0 C), following a more constant period even if the sun was already gone for almost an hour.

After this the descend is more natural until 2:57 AM when it reached 39.4 C, the lowest temperature of the night. Before 5 AM it was a strange rise from the already very high base to 40.9 C, then started to drop again. The lowest reading of 38.1 C happened shortly before 8 AM in full daylight, but the sun probably reach inside the gorge only later. I’ve spent this night around the lake and measured similar temperatures with my handheld device (38-40 C between 0 – 6 AM). Meanwhile the sky became cloudier.

Second day (June 22nd)

I left the area during this morning and returned only in the last day (26th in the late afternoon) to collect the equipment. This second day is a weird one as it is composed of the lowest maximum (44.3 C at 3:15 PM) sandwiched between the two highest minimums (38.1 and 37.6 C).

This and the fact that it has some shorter abrupt drops in the early evening (again between 6 – 7 PM) suggests that it was windy, another sandstorm is very likely. However the mentioned max and the min were both registered in the expected period (afternoon, respectively early morning).

Third day (June 23rd)

During this day I was on a trip around the western part of the Ghoubbet bay, so not too far from Lake Assal (25 km from the gorge). The morning was cloudier, while the midday and early afternoon sunny and very hot. I measured 46 degrees on the black lava field with my handheld thermometer, while the wind was moderately blowing.

From the morning there was a constant rise until 3:03 PM when the day’s maximum of 47.2 C was registered and the same value was reached again at 4:25 PM after a small setback. This second peak was instantly followed by a big drop of more than 3 degrees in 6 minutes, then the curve became more normal. This coincides with the time when I was finishing my hike and saw some bigger clouds forming in the north-west. Probably it was again only wind, without rain. We can also observe on this day an unnatural 3 degree warming in the evening between 9 – 10 PM (exceeding 40 degrees again), certainly khamsin. The descend happened only after midnight, while the minimum was 35.2 C in the early morning.

Fourth day (June 24th)

This day the temperature has a quite normal evolution, reaching 44.6 C at 3:07 PM following a constant rise, while after 4 PM starts the descend, which has no abrupt changes (except a slight rise in the evening) until 5:05 AM, when recording the minimum of 33.3 C. This will be also the lowest temperature of the entire measuring period.

I was in Djibouti city on this day, so I don’t have direct info about the cloud cover over the area.

Fifth day (June 25th)

On this day I was again on a trip to Ghoubbet bay, this time in the south-eastern part, thus a little farther from my study area (around 45 km). It was less haze than on the other days, from the high ledge of the plateau I could see the other side of the bay (though only barely).

This day the max was reached a little earlier than usually: 44.5 C at 2:29 PM, with a slight setback (almost constancy) afterwards, the concrete drop starting only after 5 PM with some abrupt changes in the first half hour. It was again a +2 degree rise in the evening, followed by a less constant decrease until dawn, when the minimum of 35.8 C happened.

Sixth, last day (June 26th)

Today in the late afternoon I came back to Lake Assal to collect the equipment. It was haze again with a few clouds in the sky (not clearly seen). The timing was good as I reached the gorge only after 6 PM when the temperature was already decreasing, thus having the daily maximum recorded also for this day.

The peak of 46.1 C was reached at 3:59 PM, exactly in the same minute when the first day’s 47.4 C happened. We can observe on the graph an abrupt early morning rise of 1.6 degrees, respectively a +2 degree unnatural drop after 1 PM. The rest is more or less a constant rise until 4 PM, then decreasing. The last reading was 43.6 C at 6:07 PM when the logger was stopped.

The mean temperature of the 6 days/ 5 nights measuring period in the wadi is a round 40.0 degrees Celsius, an unusually high average for sure. The mean maximum was 45.7 degrees, while the mean minimum, 36.0 degrees. The maximum is similar to the ones measured at the hottest weather stations in the world: Death Valley (Furnace Creek), Persian Gulf states (Ahvaz, Basrah, Jahra), central-western Sahara (In Salah, Reggane), Pakistan (Sibi, Jacobabad) and the Ethiopian Danakil (Dallol). The minimums seems to be higher than anywhere else on the planet, no station recording above 35 C average lows in any month.

General conclusions

• Lake Assal area is one of the hottest places on the Planet, having a similar climate with the Ethiopian Danakil, where the highest yearly average of 34.6 C was recorded between 1960-1966 at Dallol.
• The daily maximums are usually happening in the afternoon around 3-4 PM, after a more or less constant rise from the morning.
• The late afternoon/ evening hours are characterised by instability and more abrupt changes, the wind velocity being the highest in this period.
• Temperature rise of 2-3 degrees can happen at any time during the dark hours, exceeding 40 C even at dawn.
• The daily amplitude is small, especially for a tropical desert. This is caused mostly by the hot and dry khamsin wind, which mixes the layers. Clouds can keep the heated air under their blanket during night, enhancing this phenomenon.
• There are more clouds in the night and morning than at midday.

Comparison with Djibouti (Ambouli International Airport) weather station

According to Wunderground’s history, but also mentioned by my driver Houmed, the temperature in Djibouti city reached 45 degrees Celsius on 21st June (2-3 PM), when the 47.4 C peak was recorded in the gorge near Lake Assal. This is only one degree shy of the city’s absolute record and certainly was caused by the khamsin. As Ambouli’s available values are all rounded I must work with these: in 21st the difference is 2.4 degrees in favour of Lake Assal.

Also 22nd was a very hot day in the capital, when 44 C was measured in the same early afternoon interval. As I spent this day in the city, I can confirm from personal experience that the heat was extreme indeed. More than that, this day the two peaks were very similar, my logger measuring its lowest maximum in the gorge: 44.3 C

On 23rd the difference is bigger, the city recording 42 degrees, while Lake Assal 47.2 C: 5.2 degrees. June 24th was the “mildest” day in the capital with only 37 degrees (but likely with high humidity), while my station recorded 44.6 C: 7.6 degrees difference, the biggest one. On 25th the discrepancy is smaller again, Djibouti reaching 41, while Lake Assal 44.5 C: 3.5 degrees. In the last day, on 26th, the disparity is again high: 39 vs 46.1 C: 7.1 degrees.

The average difference between the maximums for the six days is 4.3 degrees in favor of Lake Assal. Due to the coastal placement Djibouti is usually more humid with a high heat index even with only 35-36 degrees Celsius, while Lake Assal is much more affected by the dry wind.

Comparison with Dallol (Ethiopian Danakil)

As Dallol weather station operated only between 1960-1966 and the datas are also kind of questionable, this comparison will be less concludent.

If we take into consideration the month of June, Dallol’s mean maximum is one degree higher than the average max of my six day research near Lake Assal: 45.7 degrees. However, I have some doubts regarding Dallol’s value, which compared to its absolute June max looks unusually high: only 1-1.5 degrees difference between them. That’s just too small even for 6-7 years of measurement. As I saw a lot of suspicious climate charts and tables in my life with significant differences even between the same locations, my general opinion is that many of them is based on algorythms and are not coming from real, ground based measurements.

Final question: Could Lake Assal’s depression beat the actual World Record for the highest temperature? We could not exclude this, but my opinion is that the upper limit must be somewhere between 50-52 degrees Celsius here. I think there are more chances to beat the highest low temperature for one night, the actual record being 44.2 degrees Celsius in Khasab (Oman).

I consider this research a successful one, actually it’s the first one flawlessly completed with all days and nights correctly monitored.

Journey photo album

To be continued…

Intro: the warmest capital city

Together with Khartoum in Sudan, Djibouti city is the hottest capital in the world, having a yearly average temperature just a little shy of 30 degrees Celsius. While the “winters” are warm (kind of an european summer), the hot season is sweltering and the high humidity, characteristic for the coastal areas make the tropical ambience even more oppressive. The heat doesn’t go away even in the night, thus the living is very challenging without air conditioning, especially for non-natives. In the dark it almost feels unreal, like you are trapped inside a giant sauna without walls.

The city has a population of around 600.000, represented mostly by issa (somali) and afar ethnic groups with some arabs, french and other minorities beside. The former french colony is a busy strategic port close to the Red Sea’s Bab-el-Mandeb strait and more countries have military bases here. Before known as “French Somaliland”, after gaining the independence in 1977 the small country received the same name as its capital. Unknown for many travelers, the tourism is not very well developed here, but is rising in the recent years. Security is taken seriously, police presence is common. Djibouti’s downtown is quite noisy, with many honking green/ white taxis and old minibuses looking for the next passenger. Ambouli International Airport is close to the city and greeted me before midnight on June 18th with the first dose of african heat.

Choosing the target

The most iconic place associated with heat in the meteorological sense is undoubtedly the Sahara desert. An endless, empty place with the size of a continent presenting huge, sunbaked sand dunes and barren, rocky terrain. Temperatures are known to be very high there, often exceeding 50 degrees in the shade. Wait. Is this really true? Well, partially. Actually there were only a few cases when reliable temperatures above 50 degrees were measured here, the 51.3 degrees Celsius recorded in Ouargla (Algeria) on 6 July 2018 being the most certain one. Some old readings like the famous 58 degrees from El Aziziya were infirmed in the later years after specialistic investigation of the used equipment and measuring conditions. Long story short: naturally occuring +50 C air temperature is less common than people think.

Regarding my personal research, from the three main extreme categories (Cold, Heat, Amplitude) heat was the last to come. Actually it’s not exactly the first time, a few years ago I’ve visited the Ethiopian side of the Danakil depression with the same purpose, but the research was unsuccesful as I couldn’t collect the equipment from an inactive volcanic crater because of … let’s say “bad luck”, having to deal with unreliable local collaborators. Thus it’s understandable that I felt a strong need to come back to the Danakil and “finish the job”.

The sunken desertic area of tectonic origin is situated on the territory of three countries: Ethiopia, Eritrea and Djibouti. While the first one has the biggest portion, Djibouti owns the lowest spot, represented by the shores of Lac Assal at 155 meters below the sea level, also the deepest land in Africa and second in the world after the Dead Sea’s depression*.

While second to the Dead Sea regarding the elevation, the raport between the two is reversed when we are talking about the salt concentration, Lake Assal being the saltiest lake of considerable size in the world (ten times more than the ocean), surpassed only by two small ponds (one in Antarctica, the other also in the Danakil), so one can easily float on the surface without sinking.

I have an old passion for below sea level places, which usually have a very hot climate (Death Valley in the USA is the best example). Why? There are two main reasons for this: first because of the general rule that normally temperature drops with elevation (6.4 degrees by 1 km), secondly because these places are parts of very dry, desertic environments, strong evaporation being a basic condition for their formation. A consequence of the latter is that they are often associated with salt marshes, the residue of the former lake. Badwater in Death Valley (-86 m), the southern part of the Dead Sea (around -400 m), Aydingkol in the Turpan Basin (-154 m) and Lake Assal (-155 m) all have these same two things in common: salt flats and extreme summer heat.

Dallol in the Ethiopian Danakil is considered to be the place with the highest average temperature in the world with a whopping 34.6 degrees Celsius, according to the short period of measurements from 1960 to 1966. June is the hottest month with a mean maximum of above 46 degrees, very similar to the well known “heavyweights” of the domain like Death Valley, the Kuwait-Iraq-Iran border area near the Persian Gulf (July-August) or the Jacobabad-Sibi plain in Pakistan (May-June). However, unlike the former mentioned ones which all reached 52-54 degrees at a certain time, no temperatures above 50 were ever recorded in Dallol, 48.9 C being the highest measurement. An unusually small gap of less then 3 degrees between the typical and the extreme values for sure, even for only 6-7 years of data. The heat is “at home” here, it’s never coming from somewhere else as in the case of most places (like Saharan origin heat in Europe for example), this must be the main reason for this constancy.

While before I’ve chosen the more interior part of the Danakil (Afdera Lake area) to completely avoid the moderating effect of the sea, now I knew that Djibouti’s Lac Assal is definitely not “too close” to the coast as in the summer months the wind (known as Khamsin) is blowing from the land, heating and drying everything on its way. The difference between the two regions is in the cooler part of the year when the wind is coming from the east (Indian Ocean), internal areas remaining warmer than coastal ones. Lake Assal’s southern shore is situated only 10 km away from the Ghoubbet-el-Kharab bay, an almost completely closed part at the very end of the Gulf of Aden. Actually the highly saline lake gets its water from this bay through the tectonic fissures.

The general area was defined, let’s look at the small scale features. Basically I want to set the equipment at a little distance from the lake (respectively the salt pan) to have such ground below, which can heat up more (sand or gravel). Beside this I try to identify some topographical enhancement, without loosing too much elevation. After looking thoroughly everything around on GoogleEarth I found the right spot inside a gorge, just a few hundreds of meters from the salt flats. The dried riverbed’s name (known as “wadi” or “oued” in the arab world) is Kadda Galeita. Regarding the elevation the satellite data is not so precise here because of the small sizes, thus I partially concluded from the visual aspects that this place must be the best one for my purpose. Beside the general “canyon effect” (part of the solar radiation is reflected back by the walls), the concave curvature of the gorge is looking exactly to the NW, from where the strong sun will strike the slope in the early afternoon hours. Despite being on the Northern Hemisphere, because it’s inside the tropics, in this period of the year the sun passes slightly to the north above the land and June 21st is when the northern deflexion is the biggest.

In Djibouti the meteorological measurements are scarce. It seams that outside the capital’s airport there are no other weather stations at all, anything else is based on hypothetical approximations (both the regional forecasts and the climate diagrams). The city’s highest recorded temperature is 46 degrees Celsius (June and July), also just a few degrees above the summer months average maximums (40-42 degrees), a characteristic of the lower latitudes.

At present industrial scale salt extraction is happening at Lake Assal, consequently in the recent years can be reached on paved road. However the area is still kind of remote as there is no public transport from the Tadjoura main road, usually only expensive private tours and taxis are taking the tourists there. My target is about 10 km far from the “parking lot” (the end of the asphalt road).

*The Sea of Galilee (-212 m) often mentioned as the second lowest basin in the world actually is a part of the bigger Dead Sea depression. They are linked by the Jordan river, so can’t be considered a separate basin. However it is the second lowest lake.

Brief summary of the research

I arrived in Djibouti on June 18th in the late evening and after two days of rest and some acclimatization in the muggy heat of the capital, in the early morning of June 21st I was heading with a private driver to Lake Assal, which lies about 110 km west from the city.

After leaving the main Ethiopian road with heavy truck traffic, we continued on the Tadjoura way around the gulf of Ghoubbet, then turned left and reached the end of the asphalt road on the lake’s southern shore after 8 AM. From here I started the hike on the salt pan towards the target situated inside the gorge.

The weather was already hot and became oppressive while reaching the exact location in the wadi after 10 AM. There were only a few clouds, but the characteristic summer haze caused by the hot and dry khamsin wind was present. However, I felt only weak air movement until now.

The bubble-aluminium foil protected data logger (I positioned the device’s screen to face south) and the Barani solar radiation shield under which its sensor was sheltered were mounted on a tripod whose legs were farther stabilized with nearby rocks.

The exact coordinates are: 11.686346 N, 42.341225 E, the elevation around -130 meters. The height of the sensor from the ground is 160-170 cm. At 10:43 AM the mini weather station started its operation. First reading: 42.4 degrees Celsius.

I waited in the shade nearby the research equipment until late afternoon, meanwhile checking the temperature more times and measuring also the ground in the early afternoon. With some luck I caught the highest air temperature live: 47.4 degrees Celsius around 4 PM and saw 73.9 C on sandy surface around 1 PM. The sky was partially covered in the hottest period, but the clouds coming from the NW never managed to block the sun.

After a sandstorm, which hit my camp in the early evening, I’ve spent the following night outside, hiking back to the asphalt road until the morning were my driver picked me up. The evening and night was still extremely hot, this phenomenon felt even more outlandish than the peak heat of the day.

I couldn’t sleep or even rest until dawn as the temperature never dropped below the human body’s and the hot wind was making the real feel even worse. Meanwile the sky became cloudier. This night’s minimum temperature in the gorge was 39.4 C !

I’ve spent the next days sleeping in the city with two separate trips to the Ghoubbet-el-Kharab bay using public transport: one to the volcanic area with new lava fields on the western side of the gulf and one to the higher plateau on the south-eastern part. Because of the proximity to the ocean, the capital is much more humid than the internal areas, having the heat index higher for the same temperatures. Here you are constantly sweaty, while at Lake Assal the khamsin sucks out all moisture from you.

I returned to collect the equipment on 26th in the late afternoon (haze again) and found the tripod standing in its place on the wadi’s floor with the logger functional and everything intact. The research was successful, all data was correctly recorded. The first day’s 47.4 degrees wasn’t surpassed on any other day, but was approached on 23rd with 47.2 degrees. The lowest daily maximum was 44.3 on 22nd, while the minimum of the entire measuring period 33.3 degrees Celsius in the morning of 25th.

During my staying in the Lake Assal area I didn’t encountered any wild animals outside of four camels and hearing some high pitched bird noises inside the gorge. The vegetation is completely missing on the salt flats and is also very scarce on the sandy-gravel surface. No acacia trees, only some small tufts. At the end of the asphalt road live some locals (mostly youngsters) who sell salt and other mineral related souvenirs and there is some activity at a chinese salt extraction plant. No other tourists were present as it is low season because of the heat.

The instruments used on the field

-One LogTag UTRED30-16 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 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…