RAINFALL AND RAINY DAYS IN THE HIMALAYA WEST OF NEPAL

LIEUT.-COLONEL KENNETH MASON

I have been led to examine the figures published by the Indian Meteorological Department for the rainfall and number of wet days at selected Himalayan stations by the frequent occurrence in the accounts written by recent Himalayan travellers of such phrases as 'abnormally late snowfall’, Unexpected break in the weather', and so on. The graphs published with this paper may therefore be of interest and are intended to show at a glance the normal, or expected, weather at certain stations, as far as there can be such a state as normal weather. I shall not attempt to explain the causes of the various periods of wet weather.

It must be remembered that many of the stations are sited in valley bottoms, and that more rainfall, or snowfall, and more wet days are encountered on the surrounding hills; but for obvious and practical reasons it is not possible to maintain regular weather stations high up on the main ranges. Figures relating to valley stations, therefore, can only give a very general indication of the periods when fine or wet weather may be expected on the hills.

All the stations examined are west of the meridian of western Nepal, from Champawat and Pithoragarh on the east to Chitral, the westernmost. One group of stations in the plains of the Punjab has been included in order to show the periods of rainfall when the effects of mountain topography are absent. At each station the Survey of India map reference, the approximate altitude, and the annual normals for rainfall and rainy days are given. The graphs show the amounts of normal monthly rainfall joined up by continuous lines, and the monthly normals of rainy days joined up by broken lines. Important monthly maxima have been indicated by figures, rainfall figures being underlined. The data have been taken from Memoirs of the Indian Meteorological Department, vol. xxiii, part vii. It may be remarked that a rainy day is one on which there is at least one-tenth of an inch of rain. A foot of snow is approximately equivalent to an inch of rain.

The same unit for an inch of rainfall has been used for one rainy day. This has the advantage that, with certain reservations, one can estimate by comparison the heaviness of the monthly rainfall. For instance, where heavy tropical rainfall is experienced the rainfall graph rises above that of rainy days, showing an average of over one inch a day, in some cases for as many as twenty days in the month. Elsewhere the graph for rainy days is often considerably above that of rainfall, showing a less tropical form of rainfall, or a period of snowfall.

The stations have been arranged in ten groups, as follows:

1. Stations in the Punjab plains from Jullundur to Rawalpindi, thence to Attock, Peshawar, and Landi Kotal (Figs. 1-7).
2. Lesser Himalayan (outer Pir Panjal) stations in Jammu (Figs. 8-12).
3. Outer Pir Panjal stations in Punch (Figs. 13-17).
4. Murree and the Jhelum valley to the Vale of Kashmir (Figs. 18-22).
5. The Vale of Kashmir and the Great Himalaya by the Zoji La (Figs. 23-30).
6. Gilgit, Skardu, Kargil, and Leh, beyond the Great Himalaya (Figs. 31-4).
7. Malakand and Chitral, the extreme north-west (Figs. 35-7).
8. Stations in the Lesser Punjab Himalaya (Figs. 38-47).
9. The Simla and Mussoorie Lesser Himalaya (Figs. 48-54).
10. Garhwal, Naini Tal, and Almora hills (Figs. 55-67).

There are a few characteristics common to all, or nearly all, stations examined. The finest month, that is, the one with fewest rainy days and with the smallest amount of rain, is, for every station south of the Great Himalaya, whether in the Himalayan valleys, on the hills, or in the Punjab plains, the month of November. Wet days are extremely rare and, as we all know, the mountains stand out for the greater part of the month clear of cloud. It is the best month for travel and photography in the valleys, and but for the shortness of the days and for the night cold it would be the best month for high- altitude climbing; it is ideal for surveying the lesser Himalaya.

Generally speaking, there are two periods of wet weather, the winter rains and the south-west monsoon. The greater part of the monsoon rainfall that reaches the Himalaya is brought by the Bay of Bengal branch, the moisture-bearing winds being deflected by the Himalaya north of Bengal north-westwards up the Ganges plain. A much less amount of rain is brought direct by the Arabian Sea branch. These facts are shown on the graphs by the greater monsoon effects in the east than in the west. The winter rains, on the other hand, come from the west, and the effects of these western currents are greater in the west than in the east. These generally begin to influence the figures for December more markedly in the west than in the east. After these rains April is generally the finest pre-monsoon month eastwards of Simla, but the 'winter rains⁵ last considerably longer in the west and often reach a maximum here in April. This is particularly noticeable in the Vale of Kashmir and in the neighbourhood of the Great Himalaya in Kashmir. As is to be expected, the monsoon begins normally earlier in the east than in the west and rises to a much higher maximum. The rain-shadowing effects of the outer ranges are more noticeable on the amount of rainfall at valley stations in the hills than on the number of rainy days. The high Pir Panjal range has a very marked rain-shadowing effect on stations in the Vale of Kashmir, though a much greater number of wet days is experienced on the hills north of the Vale than the valley figures appear to indicate.

The monsoon lasts from about mid-June to the latter half of September in a 'normal' year, with peaks in July or August. Occasionally it lasts into October, though generally this month is almost as fine as November. The October days being longer than those of November, and the nights less cold, climbing at moderate altitudes is very enjoyable in Kashmir during October.

The following notes deal in greater detail with the conditions at each group of stations.

Stations 1-7. Punjab and Peshawar Plains.

Jullundur, Sialkot, Jhelum, Rawal Pindi, all in the plains of the Punjab, show little variation from each other, though the amount and heaviness of monsoon rainfall decreases slightly as one goes westwards. At Attock and Peshawar the monsoonal effect is considerably less, while at Landi Kotal, in the Khyber, where the monsoon is negligible, the effect of winter disturbance is more marked. There are, in fact, as many as 12 wet days during March and April in the Khyber, and 6 out of its normal annual 15 inches of rain fall during these two months (Fig. 7).

Stations 8-17. Jammu and Punch.

These stations are in the outer hills of the Pir Panjal range of the Lesser Himalaya, or at their foot near the edge of the plains. The Pir Panjal rise to over 15,000 feet and act as a barrier to monsoon currents.

Jammu (Fig. 8) and Bhimbar (Fig. 13), both at about 1,100 feet above sea-level, are at the extreme foot of the hills, as is Mirpur, 1,200 feet (Fig. 14), a little to the north-west. They show little difference from stations such as Sialkot and Jhelum (Figs. 2 and 3). Udhampur (Fig. 9) at 2,350 feet, Riasi (Fig. 10) at 1,700 feet, Ram- pur Rajauri (Fig. 15), 3,100 feet, and Kotli (Fig. 16), 2,000 feet, are all behind the low outermost hills, but not rain-shadowed by them. They therefore show a heavier rainfall and more rainy days than the outer stations, more in the east than in the west during the monsoon period, and there is a close similarity between the winter rains at all these four stations.

Bhadarwah (Fig. 17), 5,400 feet, Ramban (Fig. 12), 2,300 feet, and Punch (Fig. 17), 3,300 feet, are all behind the outer range of the Lesser Himalaya, but south still of the Pir Panjal. They show the effect of rain-shadowing from the southerly currents of the monsoon period, but also exhibit their exposure to the westerly currents of the winter rains. It should be remembered that these stations are in valleys in the hills. In summer a much greater rainfall, and in winter a heavy snowfall are experienced on the neighbouring hills. It is the snowfall from January to March, with late falls in April, that blocks and closes the passes of the Pir Panjal

Stations 18-22. Jhelum Valley.

This group of stations are on the line of the Jhelum valley entrance to Kashmir, Murree at a height of 7,000 feet on a line of hills trending from NNE. to SSW., Muzaffarabad and Domel low down near the junction of the Kishanganga and Jhelum, at the great syntaxial bend of the latter, Uri and Baramula beyond the gorge which the Jhelum cuts through the axis of the Pir Panjal.

Murree, owing to its position athwart the monsoon currents, receives considerable rain during the monsoon months, Muzaffarabad and Domel less during the same period, but more during the winter and spring, while both Uri and Baramula show the marked effect of the Pir Panjal rain-shadow. The Pir Panjal rises to over 12,000 feet immediately south of Uri, though there is a gap known as the Haji Pir pass as low as 8,652 feet in the neighbourhood. It rises to 14,000 and even 15,000 feet south of Baramula. The actual amount of rainfall at both Uri and Baramula hardly increases during July and August, though at Uri, probably owing to 'leakage' through the Haji Pir, the number of rainy days rises to a secondary maximum. The maximum for both rainfall and rainy days for these two stations is in March, with little diminution in April, a feature that is also present as secondary maxima at Muzaffarabad and Domel, though overshadowed by later monsoon rain. Any one who has travelled the Jhelum valley road at all seasons of the year will remember how often the road is broken by slips during March and April.

Stations 23-30. The Vale of Kashmir.

The stations in this group show to different degrees the same features as those of Baramula. Figures for the whole year are not available for Gulmarg, at 8,700 feet on the northern slopes of the Pir Panjal. Here, at Gulmarg, the monsoonal effect is marked, but the separation between the curves for rainfall and rainy days shows that the rainfall is nothing like as heavy as that experienced south of the Pir Panjal. Nearly a third of the days in July and August are wet, but the rainfall for these two months is under 9 inches. The last half of September, October, November, and early December are almost rainless, but snow falls as a rule during the last month of the year, and parties of skiers go to Gulmarg for winter sports at Christmas time. No official figures are available, but the writer, who has been to Gulmarg in every month except May, November, and December, believes that complete curves for the year would show a marked maximum for both rainfall and rainy days (in the form of snow) in March, or possibly April.⁹

 

The graphs for the five stations Sopor, Srinagar, Avantipur, Anantnag (Islamabad), and Kulgam (Figs. 24-8) show the small effect of the monsoon in the open Vale of Kashmir, though at the last three, where the Vale is narrower, the monsoonal effect is more marked than at the first two. All five show the rainy-day maximum in April. Climbing and exploring expeditions waiting to get away from Srinagar in April or May frequently complain that 'unusually late' falls of snow on the passes, or rain in the valleys, or floods in the rivers, cause delay to them. In actual fact these 'late' falls are normal, as will be seen from Figs. 24-7, and more obviously from Figs. 29 and 30, which show the conditions at Sonamarg and Dras, the former on the Kashmir side of the Great Himalaya, the latter two marches beyond.

The conditions in Kashmir are, in fact, markedly different from those in the outer hills south of the Pir Panjal. Not only is the actual monsoon rainfall considerably lower, but the average per day during the monsoon period is much less, as shown by the separation of the two graphs between June and September.² The stations show the very marked minimum in November, a rapid rise at the end of December and during January, then a slower rate of increase to the April maximum. The fall is of very great importance, for, even as late as April or May, it lies as snow and does not run off as surface water to any great extent. Subsoil water supplies are thus replenished as well as glacial reservoirs. The higher and later maximum for the 'winter rains' seems to be due to a more northerly course of the western disturbances during this period.

The comparison between the two graphs 29 and 30 is of great interest, because they illustrate the only two stations observed closely on either side of the Great Himalaya. Both show a high maximum of rainy days in March, though the fall is almost entirely of snow in both cases. At Sonamarg nearly 15 inches of rain (approximately 15 feet of snow) fall in the 15 wet days. At this period all precipitation at Dras is snowfall, and the whole route between the two places is heavily snowed up. Fine days, however, occur in spells of 4 or 5 days at a time, and it is then possible and, after 48 hours of fine weather, safe to cross the Zoji La (pass) with a large caravan, provided a start is made before midnight and the crossing completed in the very early hours of the morning. In early May, when normally there are actually fewer wet days, conditions may be more dangerous owing to a higher temperature. The graded road over the Zoji La is not free of snow in a normal year till the end of May, until when caravans have to take the route up the snowed-up valley bottom.

The effect of the Great Himalaya is at once obvious by a comparison of the graphs for the monsoon period at Sonamarg and Dras. Sonamarg shows for July and August eight wet days each month, but less than 4 inches per month; that is, when it is wet at this period the rain is not heavy. At Dras the months of minimum rainfall and of fewest wet days throughout the year are July and August, lower even than in November.

Stations 31-4. Beyond the Great Himalaya.

Gilgit, Skardu, Kargil, and Leh may be taken as typical valley stations of the great longitudinal troughs beyond the Great Himalaya. In every case the annual precipitation is less than 10 inches— at Leh as little as 3-2. Gilgit, Skardu, and Kargil show the effects of winter disturbances; at Gilgit these may be marked as late as May, though at Skardu and Kargil March and April are the worst months. Leh, owing to the absence of winter rainfall, shows a maximum during the monsoon months, but with so low an annual precipitation this has little significance. There is, of course, considerably greater rain and snow on the surrounding mountains, and the main pass over the Ladakh range immediately north of Leh, the Khardung, 17,600 feet, is rarely open to yak transport before the middle of June; while, though all these stations show very little rainfall during the monsoon months, monsoon incursions most certainly reach the higher mountains during July and August, and even occasionally pass northwards beyond the Karakoram.

Stations 33-7. Malakand and Chitral.

It is interesting to consider the late western disturbances by an examination of stations immediately west of Kashmir. Malakand is situated at a gap in the North-West Frontier hills overlooking the plains of Mardan on the south and east and the Swat valley on the north. By reason of its position and altitude it shows a rainfall maximum of about 9 inches in August, due, apparently, to the monsoon, but there is a greater period of liability to wet weather from January to April, with a secondary maximum in March, due to westerly disturbances. Of the annual rainfall of 37-3 inches, 14 occur in July and August and 16 from January to April.

The valley of the Kunar in Chitral is rain-shadowed from all direct monsoon influence by the 10,000-foot Hindu Raj range. Drosh and Chitral each have their maximum in March and almost all their precipitation occurs between the months of January and April. There is, however, a curious late period of disturbed weather during October which does not seem to be due to monsoon conditions. It is interesting to compare Chitral conditions with those of the Vale of Kashmir (Figs. 22-8).

Stations 38-67 are all east of Jammu and Kashmir and west of Nepal, and all are south of the main axis of the Great Himalaya. They may be divided into groups as follows:

1. The Punjab hills west and north of Simla.
2. Simla and the Mussoorie hills.
3. Garhwal.
4. Naini Tal and Almora districts.

Stations 38-47. The Punjab hills west and north of Simla.

Hoshiarpur and Gurdaspur, in the plains at the foot of the hills, are included for comparison with hill-stations. The former is about twenty miles north-east of Jullundur (Fig. 1), the latter about fifty miles north of it. The graphs of all three stations are very similar to each other. Kangra and Pathankot lie in the broken Siwalik country, the former north of the Siwalik hills at about 2,300 feet, the latter in the plain between the Beas and the Ravi, where the Siwalik hills are almost absent. Kangra shows the increase in rainfall due to its hill position, while the weather of Pathankot is not dissimilar to that of Gurdaspur.

Palampur and Dharmsala are two stations over 4,000 feet on the southern slopes of the next range of the Lesser Himalaya—the Dhaula Dhar—which rises immediately north of them to a height of over 15,000 feet. Both show the considerably higher monsoon rainfall due to their altitude and open situation facing south. Palampur receives 81 and Dharmsala 95 inches of rain during the monsoon months out of annual totals of 101 and 115 inches, respectively. Both are affected by winter disturbances, but the effect is overshadowed by the summer maxima.

Dalhousie, a Punjab enclave in Chamba State, is higher than Palampur and Dharmsala, and on the lowered axis of the Dhaula Dhar range before it sinks to the passage of the Ravi. The valley of the Ravi also skirts this station on the north, while it is rain-shadowed to some extent by outer hills. The effect is shown by a smaller, though still considerable, monsoon rainfall.

Banjar, in the Tirthan valley, Kulu and Nagar, in the upper Beas valley, are all valley stations north of the hills enclosing the Sutlej. Consequently their annual rainfall during the four monsoon months, June to September, amounts to only 25, 18, and 22 inches, respectively, though the number of rainy days is considerable during that period (40, 27, and 39, respectively). There is a marked contrast between the comparative lightness of the monsoon showers of these three stations and the heavy continuous rainfall of outer stations such as Palampur, Dharmsala, and Dalhousie.

Stations 48-34. Simla and Mussoorie hills.

The conditions at stations of this group are so well known as to require the briefest mention only. The differences between the rainfall at the various stations are largely accounted for by local situation. The Kasauli, Simla, and Kotkhai stations are considerably northwest of the Chakrata-Dehra ones, consequently their rainfall is generally somewhat less. Simla, farther in the hills than Kasauli, has a slightly higher rainfall, mainly from winter depressions, and more wet days during the monsoon, due to its exposed situation on an east-west ridge, as compared with the north-south ridge on which Kasauli stands. Kotkhai, though due east of Simla, is relatively farther in the hills, and is rain-shadowed by the 9,ooo-foot Dhadi Dhar ridge.

The effect of the low Siwaliks is to condense the moisture of the monsoon currents rather than to rain-shadow the Dun north of them; but though Dehra gets a considerable rainfall during the monsoon, the sudden rise from the Dun to the east-west ridge at Mussoorie brings a still greater fall to Raj pur. At the same period at Ghakrata, farther in the hills, the rainfall already shows a decrease, about 53 inches at Chakrata compared with 81 at Mussoorie and 105 at Raj pur for the monsoon months.

Stations 55-61. Garhwal.

The stations in Garhwal also illustrate the local importance of topography. Kotdwara (Fig. 55) at the foot of the hills, and Lans- downe (Fig. 56) on them, where the Siwaliks are close pressed against the Lesser Himalaya, are comparable with Dehra Dun and Mussoorie, respectively, both as regards topography and rain conditions. Pauri (Fig. 57), just north of the crest of a 7,000-foot ridge enclosing the Alaknanda valley on the south, and Srinagar (Fig. 58), north of it low down in the Alaknanda valley itself, show the effects of local rain-shadowing, both in amount and heaviness of precipitation. Karnaprayag (Fig. 59), at the junction of the Pindar and Alaknanda, though farther in the hills than Pauri, shows a slightly greater rainfall, probably due to its very enclosed situation.

Joshimath (Fig. 60), at the junction of the Alaknanda and Dhauli, and Okhimath (Fig. 61), in the Mandakini valley, are interesting to compare. The first is rain-shadowed on the south by the southernmost crest-zone of the Great Himalaya, a north-west extension of the Trisul crest-alinement, while Okhimath lies in a valley open to the south and backed on the north by the Kedarnath-Badrinath section of the main range. Okhimath, therefore, receives far more monsoon rain than Joshimath, 44.8 inches in July and August compared with 15.8. On the other hand, Joshimath has a higher and later maximum for 'winter' rain than Okhimath, 4.8 in March and 3-8 in February, as against 2.8 and 3.2, respectively. These two stations are of particular interest owing to the paucity of stations in the neighbourhood of the Great Himalaya.

Stations 62-7. Naini Tal and Almora districts.

The last group is the easternmost of which we have records west of Nepal, and their main interest is in a comparison with stations east of Nepal. They show most of the same features as those of Garhwal. Kathgodam (Fig. 62) is, like Kotdwara (Fig. 55), at the entrance to the hills; Naini Tal (Fig. 63) is comparable with Lansdowne (Fig. 56), high up in the outer hills. Their respective charts are closely similar, though the amounts of rainfall are slightly greater at Kathgodam and Naini Tal than at Kotdwara and Lansdowne, probably owing to the more easterly situation.

Ranikhet (Fig. 65), behind the outer hills and rain-shadowed by the 8,ooo-foot Gagar ridge, immediately shows the lower monsoon rainfall due to its more sheltered situation. Almora (Fig. 64), still farther in the hills, is comparable with Pauri (Fig. 57) or Srinagar (Fig. 58). Ghampawat (Fig. 66) and Pithoragarh (Fig. 67) are somewhat similarly placed to Ranikhet and Almora, and there is little to notice about their rainfall.

It is very obvious that for climbing, or even for valley travel, except in the open but rain-shadowed Vale of Kashmir, the best seasons south of the Great Himalaya are from April to mid-June, and from mid- September to the end of November. The fewer hours of daylight and the colder nights limit the effectiveness of the post-monsoon period for prolonged and high climbing. Though the monsoon sometimes affects the weather north of the Great Himalaya, considerable periods of fine weather may be expected in the monsoon months, and owing to the later falls from western disturbances, little high climbing can be attempted before June or July. To reap the full benefit of these fine weather months beyond the Great Himalaya the passes must be crossed in early May, at a time when the passes may not be officially open and when rates for transport are therefore high. Where possible, it is consequently advisable to forward equipment and supplies over the passes during the autumn preceding the year when an elaborate expedition is contemplated.

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