Lake Assal: nothing cool, but still cool (3/3)

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

The temperature curve of the 6 days/ 5 nights research period. The device was registering a value every 2 minutes (zoom in for better view)

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.

The temperature curve of the first day and the following night

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).

The temperature curve of the second day and the following night

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.

The temperature curve of the third day and the following night

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.

The temperature curve of the fourth day and the following night

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).

The temperature curve of the fifth day and the following night

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 temperature curve of the sixth (last) 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.
The satellite images of Djibouti taken on June 21st (left) with khamsin effect vs June 11th (right) with normal sky

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.

The temperature curve of Djibouti weather station on June 21st (Wunderground/ History)

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.

Weather statistics for Dallol (Wikipedia)

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.

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