WEATHER CONDITIONS ON NANGA PARBAT, JULY 1934

KARL WIEN

The German Himalaya Expedition, 1934, to Nanga Parbat was afflicted by a weather catastrophe, of which three Europeans and six native porters were the victims. Herr Wagner,⁷ who has attributed this storm to the advance of the monsoon, had previously, before the departure of the expedition, already suggested that the summit should be reached in early July, i.e. prior to the break of the monsoon in Kashmir. Basing his argument on the air currents during the monsoon period, which he had developed at an earlier date,⁸ he had shown that Nanga Parbat—in contrast to the inner regions of Kashmir—may be reached, because of its greater elevation, by the east and south-east winds flowing on the northern side of the north Indian low-pressure zone along the southern slopes of the Himalaya. It therefore may be assumed that the forces of the monsoon were active in this storm.

 

While working out the results of the last Nanga Parbat expedition and while considering at what time of the year a new expedition might encounter the most favourable conditions and be preserved with some certainty from a similar catastrophic storm, we endeavoured to examine carefully the genesis of the break of the weather on the 7th July 1934 on Nanga Parbat.

With the recommendation by Professor von Ficker I applied to the Director-General of Observatories, India, with whom already some members of the 1934 expedition had been in touch. Dr. C. W. B. Normand has kindly favoured us by putting at our disposal all the material necessary for the purpose, and we wish to express again our indebtedness to him for his kindness.

This material comprised:

1. Daily Weather Reports for India, with weather maps and morning observations of air pressure, direction and speed of ground winds, temperature and humidity, clouds, and rainfall —all from a great number of Indian stations.
2. Some further data of rainfall from Kashmir and Punjab stations.
3. Pilot balloon data (1st to 12th July) for heights of 2, 3, 4, and 6 km. for Quetta, Peshawar, Lahore, and Agra.

From these data it is possible at once to confirm Wagner's theory that there exists a relation between the break of the weather on Nanga Parbat and the advance of the monsoon. By the daily weather reports it is clearly evidenced that the monsoon was active in northwest India, in Rajputana, in the Punjab, and in Kashmir, transporting into these regions great masses of warm and humid air.

Besides, there is marked evidence that at the same time or shortly after this passing activity of the monsoon in the extreme north-west of India a western depression crossed the region, causing the warm humid air to ascend along the surface of gliding of the cold front of this depression, with the consequence that these warm and moist air masses discharged a large amount of precipitation.

The simultaneous existence and interaction of these two factors can be well recognized from the available material of observation. In my opinion this is a typical example of weather conditions prevailing in north-west India during the monsoon. It is, therefore, not without interest to investigate still further this practical example and to trace its causes, because it may be instructive not only to the meteorologist, but to any one who has to handle Himalayan problems.

1. Activity of the Monsoons.

From the existing daily weather reports of the Indian Meteorological Department it can be seen that the monsoon was active in the northern Punjab hills as well as in the North-West Frontier Province, and on the 7th July had reached a stage of farthest advance towards Kashmir and the Nanga Parbat region. The Punjab hills are sub-Himalayan ranges facing south-west, while their northern portion rain-shadows the interior of Kashmir from the air currents prevailing above the Plains.

The daily weather reports state:¹

July 1. Monsoon is strongly active in the Punjab hills.

These reports show that the monsoon invaded the north-west Indian hills and Kashmir for a short time; according to Indian meteorologists, such an invasion never prevails for a long time, and this is also confirmed in the present case; after a few days the invasion was followed by retreat to the plains of north-west India.

A closer inspection of the weather maps for each of the forenamed days indicates also the activity of the monsoon and shows that it developed in the manner described. Above all the maps show that after the 5th July the distribution of pressure over the region in question was particularly favourable for the development of south-east air currents, for while up to that day there had existed two depressions, one over Baluchistan and one over the north of the Central Provinces, they were separated by a narrow ridge of higher pressure above the plains of Rajputana; they united on the 5th July and formed one trough of low pressure stretching across the whole of the plains. In this trough the isobars were running parallel to the Himalayan range, while the pressure was rising regularly towards the Himalaya. Consequently the south-east winds prevailing on the north side of this trough of low pressure have developed from this date onwards more regularly and tended to flow alongside the slopes of the Himalayan range and up to the western ranges of the N.W.F. Province.

On the 6th July the minimum of this depression had retreated a little farther to the west. The direction of growth of pressure, that by now was more gradual, tended more to the east, and consequently winds from the south and south-west likewise found access to Kashmir.

The 7th and 8th July remained under the influence of the winds, growing in strength from SSW. in accordance with the actual advance of the monsoon. Rain increased, the isobars east of the Baluchistan depression following irregular lines trending to the south-east.

During the days following the 9th July the symmetry of the depression was destroyed; the rise of air pressure towards north-west can be traced no more, and only over Baluchistan there remained a depression which included also the N.W.F. Province and touched Kashmir.

Rainfall Stations.

The first five stations of Table 1 are on the south slopes of the Himalaya or already somewhat in the hills behind the outer ranges. Mussoorie is in the Garhwal hills, Dharampur is south of Simla, while Dalhousie and Jammu are farther north-west towards Rawalpindi, but still on the southern margin of the mountains. These five stations show that they were during the whole period of observation exposed, more or less, to the damp monsoon winds, and it was not before the 10th that there, too, with the general retreat of the monsoon, it ceased to rain.

Table i . Rainfall in mm.

 

At the two eastern stations the maximum rainfall occurred during the first days of observation; in Simla and Dalhousie on the 8th; in Jammu on the 4th July. It would appear that at these stations the monsoon was fairly active throughout the period. The strong, and for Kashmir, important, advance of the monsoon cannot be traced from these figures. On the contrary, stations in Kashmir, as well as Rawalpindi, had their maximum rainfall between the 6th and the 8th July, i.e. during the period when the official weather reports hinted at the marked advance of the monsoon. There is only one exception, Murree, which had heavy rain on the 4th July. The four stations beyond the Great Himalaya, Dras, Leh, Skardu, and Gilgit, had almost no rain during this time, which is no wonder, situated as they are in the deep narrow valleys to which the air currents have no access. The average annual rainfall at these stations is very slight (25-50 mm.); they cannot therefore provide a scale of comparison concerning the rain conditions of the country, still less of the elevated mountain regions.

2. Disturbances caused by Wandering Depressions.

The so-called 'western depressions' that, according to the definition of Mr. Sen and Mr. Chatterjee,¹ originate from south-east Europe and the Mediterranean, travel in an easterly direction and are provided with all the features characteristic of non-tropical cyclones. They bring winter rain to the Punjab, while during summer they appear when the monsoon trough of low pressure stretches over the whole of the plains. These summer cyclonal disturbances are nothing but a direct outcome of the cyclonal activity of the monsoon mechanism itself. Herr Wagner describes this system of monsoon currents as consisting of two air bodies and two air currents-a continental and a maritime one. The former is the continental air brought from the west; the maritime current flows inland from the Indian Ocean and produces near the ground what constitutes in the first line the so- called monsoon. The continental air, warmed by the land masses over which it passes, appears only at greater heights, but, owing to its greater dryness, cools more quickly and eventually becomes colder than the maritime air. The next phase of this development is a cyclonal system whose active factors are the two air bodies, while the colder continental air assumes the role of the cold sector in it. It is natural that, at a certain height above the separating surface, where the continental air has cooled below the temperature of the maritime air, there should occur heavy precipitation, as the surface of the cold air up which the damp maritime air has to glide is developed.

The development of this cyclonal disturbance is well shown by the existing data of temperature, air pressure, and of high-altitude winds.

Air Pressure.

The fluctuations of air pressure are very slight, but there is at Srinagar and Skardu, as well as at the Base Camp, a marked sinking of air pressure during the days following the 6th July. It seems fairly natural that there does not appear necessarily a direct change of pressure north of the region in which a shift in conditions of air pressure caused essentially by the meeting of the two depressions of north-west India and Bengal occurs.

Table 2. Air Pressure in mm.

 

 

 

Upper Winds. (Tables 3-6, at end of paper.)

The effect of the western disturbances appears plainest in the conditions of high upper winds above Peshawar (Table 3). On the 6th July there are predominantly south winds up to a height of 2 km., but on the 7 th there is a strong preponderance of northern and north-westerly winds. Between the 9th and the 10th July the same happened again: the southerly winds up to the height of 2 km. of the 8th and the 9th turned to northerly on the 10th. From 3 km. upwards during the whole of this period there was no material change in the direction of the prevailing winds. The sudden shifting of the winds to the north would indicate that on the 7th and the 10th a cold front passed on the rear side of a cyclone.

Less plain conditions can be gathered from the high-altitude winds of Agra, Lahore, and Quetta (Tables 4, 5, 6). At Agra we find on the 8th July up to the height of 2 km. a homogeneous south-east stream, while on the 9th the wind has everywhere changed for a northern direction. At Lahore and Quetta, however, there appears no change at all in these days, but the second change observed also at Peshawar, between the 9th and the 10th July, is well marked.

This second change in wind direction up to the height of 2 km. leads one to assume that the whole system of cyclonal disturbances, which at the end of the first week of July was strongly developed and had brought great precipitation on Nanga Parbat, was not yet finished after its first two days of activity, but remained still further active in different regions. This would also explain why the weather on Nanga Parbat still remained bad for some days. The expedition notes are unfortunately interrupted for the time of the storm and were not resumed later on, but the thermograms and the barograms for the time up to the 5th August are preserved. They show that the temperature rose again slowly from the 9th to the 14th July by about 4⁰ C., and that the air pressure remained on the low point at which it had arrived on the 7th July till the 12th July in order to rise afterwards again, but only by the small amount of less than 2 mm.

The conditions shown by the Indian weather reports are well in accordance with the mechanism of the monsoon as drawn by Herr Wagner. It is to be hoped that our knowledge of the weather conditions in the north-west Himalaya as well as in other parts of the range can be further increased by definite examples. If future Himalayan expeditions will make careful records of the weather conditions they experience the examination of all such observations collected during different seasons in the field, together with the rich material afforded by the Indian Meteorological Department, will be most important.

Table 3. Pilot Balloon Observations, 1934
Peshawar. Lat. 34⁰ 02'N. Long. 71⁰ 37' E.

 

Table 4. Pilot Balloon Observations, 1934
Agra. Lat. 27 °10' N. Long. 78° 05' E.

 

* Indian standard time.
+ Velocity in metres per second.

 

Weather Conditions on Nanga Parbat, July 1934
Table 5. Pilot Balloon Observations, 1934
Lahore. Lat. 31⁰ 34' N. Long. 74⁰ 21'E.

 

Table 6. Pilot Balloon Observations, 1934
Quetta. Lat. 30° 12' N. Long. 67° 00' E.

 

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