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Home , Lhasa, Nagqu

Elmar R. Reiter,1 J. D. Sheaffer,1 J. E. Bossert,1 Revisited—TIPMEX-86 Eric A. Smith,2 Greg Stone,3 Robert McBeth,4 and Qinglin Zheng5

Abstract compared to dust, sand, and gravel, invited the drivers to demonstrate their daring, especially during passing maneu- A long-planned field-measurement program to determine surface- vers at breakneck speeds around curves, along precipices and energy budgets at two sites in Tibet was carried out during June 1986 in collaboration with scientists from the State Meteorological Ad- over hill crests. ministration, Academy of Meteorological Sciences, People's Repub- Peasants in sheepskin coats, carrying bundles of food, hay, lic of . The data set obtained in Tibet is unique for this remote firewood, and even an occasional yak-skin boat, still popu- region of the world. The present report describes some of the expe- lated the highways. So did pony or donkey carts. But gleam- riences of the United States scientific team and its medical officer, M. Otteman of Ft. Collins, Colorado. The data are presently being ar- ing bicycles with well-dressed ladies and gentlemen pedaling chived on computer tapes. Preliminary analysis results are presented at leisurely pace, new Isuzu trucks, Nissan, and Toyota lim- as typical examples of the conditions encountered at the two experi- ousines and 4-wheelers started to clog the roads as we neared mental sites near (3635 m) and (4500 m). Lhasa, the imposing capital of Xizang Autonomous Region. The air was filled with the constant blaring of automobile horns to disperse the throngs of bicyclists, pedestrians, cattle, and sheep. The on its majestic perch on top of a 1. Return to Tibet dominating hill still gleamed with its gilt roofs, but a huge TV antenna with its Eiffel Tower shaped struts and girders now For most of the United States team (i.e. the authors of this competes as a new landmark on a smaller hill that formerly report and Merlin Otteman, a Ft. Collins surgeon and the carried the lamaist medical college. Watching television has expedition's medical officer) the 7000-m peaks and glaciers become one of the foremost communal evening pleasures in of eastern Tibet were a formidable barrier between , Lhasa. , and an unknown land of adventure, described by We gaped as we drove by the new Lhasa Hotel, replete with travelers such as Harrer, , and . For gushing fountain, Holiday Inn (and manage- the senior author the view spreading underneath the vintage ment) and a parking lot full of modern buses, taxis, and wait- Boeing 707 evoked memories of a previous journey into the ing chauffeurs. We were even more surprised as we pulled up unknown (Reiter and Reiter, 1981). Would Tibet still be the to the entrance of the spanking new Tibet Guest House (Xi- same, with dusty roads, a few old Chinese "Liberation" zang Binguan), bedecked with bunting and Chinese lanterns. trucks among pedestrians and donkey carts, curious natives The senior author's credibility, after having warned the ex- swinging prayer wheels, spartan accommodations with the pedition members about spartan living conditions, was pervasive smell of burning yak dung and rancid yak about to receive its final blow. (Fig. 1). candles? We were still unpacking suitcases when a din from fire- Stepping into bright sunshine and brisk mountain air at crackers, drums, and cymbals made us rush outside. The Lhasa Airport was a welcome relief after the muggy heat of opening ceremony for the new guest house was in full swing, and Chengdu. It was 1 June 1986, and the monsoonal with Party Vice-Chairman Mao Rubo cutting a red ribbon rains were expected soon. The old outhouse near the runway and a swarm of dignitaries suffering through interminable offered a familiar sight, but the "fragrant" adobe structure of speeches and then descending on a beautiful buffet of delica- years past had yielded to a concrete edifice of similar design cies to which we were graciously invited. Mao turned out to and unadorned functionality. There, again, were a few Tibe- be an ex-meteorologist and became a highly interested sup- tan girls giggling at the new arrivals and coyly disappearing porter of our scientific goals. Pretty Tibetan waitresses with into the outhouse if a camera was raised to the eye. But a new long, dark hair, decked out in touristic adaptations of Tibe- hotel or dormitory structure near the gate of the air field fore- tan costumes, served warm beer and cola and—lo and be- boded changes. We did not have to worry about luggage. hold—ice cubes, which did not prompt rapid trips to the There now was a downtown airline office where baggage bathroom, because they were made from boiled water. could be retrieved conveniently later during the day. We were Where had the dusty maidens of 1980 with their tangled whisked along the 60-mile road to Lhasa, now black-topped hairdos gone? (We still found them roaming around the bur- but still bumpy. The better tire traction offered by tar as geoning "free markets" and in the remote villages, but they appear to be a vanishing breed.) We ventured out into the old part of Lhasa, by taxi from 1 Colorado State University, Fort Collins, Colo. the hotel, but per pedes apostolorum back, because cabs are 2 Florida State University, Tallahassee, Fla. impossible to find once you have abandoned them. The tem- 3 Los Alamos National Laboratory, Los Alamos, N. Mex. ple in the heart of town does as brisk a business as ever, but a 4 National Center for Atmospheric Research, Boulder, Colo. new, wide and open square in front, flanked by new buildings 5 Academy of Meteorological Sciences, State Meteorological Ad- with traditional architecture, brings its role as communal ministration, Beijing, People's Republic of China. hub into better focus. Whereas in 1980 tourist were an un- © 1987 American Meteorological Society known species, hence souvenir trading was an art yet to be Bulletin American Meteorological Society 607

Unauthenticated | Downloaded 10/03/21 08:06 PM UTC 608 Vol. 68, No. 6, June 1987 learned, and souvenir hunters could hardly bag a single, overpriced item of dubious quality, now hawkers with layers of turquoise and coral jewelry around their necks descend on flocks of tourists and follow them, thrusting out their wares, quoting prices in English or punching them into their pocket calculators, inviting response bids by asking "How much?" or by holding the calculator keyboard under your nose. There are no fixed prices and lively bargaining with a street vendor immediately attracts an interested audience and competitive "merchants." Lamas selling printed prayer flags, penitents prostrating themselves in a muscle-wrenching, clockwise procession around the temple, sage brush "incense" smoldering in in- cinerators attest to the religious presence in Tibet. As in other cities in China, there now are thriving "free markets" where anything from , meat, vegetables, and clothing is FIG. 1. TIPMEX team (McBeth and Stone had already left for sold from open stalls. These markets, not present in 1980, can the U.S.). Front row: Ring Wang, Changhan Zhu, Pengju Wang, now be found even in the back country, however sanitary Yijun Liu, James Bossert, Shuhua Li, Xiepong Zhao, Yu Uang; Back conditions as well as quality of lodging and food decreases in row: Eric Smith, Elmar Reiter, Merlin Otteman, John Sheaffer, proportion to the distance from Lhasa. Wanlong Chen. Our second field station at Nagqu, a small town of about 3 000 population that spreads out on the high (4500 m) and airline officials between Beijing, Chengdu, and Lhasa, but windy plateau about 300 km to the north of Lhasa gave our eventually everything showed up intact at our point of team a glimpse of Tibet before the tourist invasion. This destination. settlement lies on the (now paved) Lhasa-- Finding suitable measurement sites was not a trivial matter highway, has a newly built hotel (without amenities) and is as and required long and arduous negotiations with officialdom. bleak as the surrounding hills. The frequent hail squalls do Besides the requirements of site representativeness and suit- nothing to cheer up the traveler. The trip between Lhasa and able wind fetch for turbulence measurements, there were ad- Nagqu is not without rewards. It leads through the Trans- ditional boundary conditions: accessibility without excessive (Nyainqentanglha Shan) with spectacular vistas commuting expenses (more difficult to meet in Lhasa than in of glacier-capped peaks, some in excess of 7 000 m, and fol- Nagqu) and site security (we ended up hiring Tibetan guards lows the upper reaches of the . The breakneck to pitch their tents, or spread out their bed rolls, inside the speed with which our drivers negotiated the bumpy road fenced perimeter of each site, thus safeguarding our ane- made the journey less enjoyable and caused damage to some mometers against conversion into prayer wheels). The Lhasa of our instruments. Working at 4 500 m is no picnic either. site was located about 300-m north of the Yarlungzangbo Sleep is difficult for lack of oxygen, and loss of appetite is as River, 10 km to the west of our hotel (or 15 km from "down- much due to high-altitude syndrome as to the limited re- town" Lhasa) on flat and open ground belonging to the sources available to the cooks. The United States and Chi- Agricultural Experiment Station. Even though not irrigated, nese teams took shifts in manning the Nagqu station. Seeing the soil was rather moist because of the high ground-water the Nagqu relief team take off from Lhasa resembled watch- table, evident from a lagoon of stagnant water approximately ing a "chain gang" being marched off to labor. The relieved 10 m to the west of our radiation instruments. The vegeta- team, on the other hand, descended on Lhasa with the same tion consisted of short, native grass serving as pasture for enthusiasm that a submarine crew would show upon a port sheep and cattle, with patches of bare soil showing through. call. This kind of surface condition is typical for river valleys in the interior of Tibet outside the irrigated and barley fields. Our site (see Fig. 2) resembled an area large enough to allow comparisons with satellite data. 2. The measurement program At Nagqu station representativeness was no problem (Fig. 3). The chosen site was located approximately 0.5 km to the Two 20-m meteorological towers, made available by the Los east of town on a surface with very short, sparse grass, and Alamos National Laboratory, were shipped in two large lichens, which, on close inspection, showed signs of frost- crates from Ft. Collins to Lhasa by boat, rail, and truck, in polygon development. The terrain was slightly inclined to- November 1985. The space in these crates was filled with wards the west. Even though the grass was sparse and short sounding balloons and various unbreakable supplies. The at the station site, it had a well-developed root system that United States team arrived by air in Beijing on 27 May 1986, inundating customs with a flood of 26 suitcases and instru- FIG. 2. (adjacent column) Panoramic view of Lhasa field site on ment crates. Red tape in China is no less a test of patience the western edge of the Agricultural Experiment Station. The city of Lhasa lies in the valley cut to the east, at a distance of approximately than in the United States. The State Meteorological Admin- 15 km. The Lhasa River occupies the valley opening to the south- istration finally ended up posting a large bond to pry our west. The valley opening to the northwest leads to Yangbajian and equipment loose from customs, to be refunded upon our into the Transhimalaya (Nyainqentanglha Shan) and holds the road leaving the country. The same baggage flood baffled Chinese- to Nagqu.

Unauthenticated | Downloaded 10/03/21 08:06 PM UTC Bulletin American Meteorological Society 609 permeated the upper 20 cm to 30 cm of soil and extended to more than 40 cm. In Lhasa, measurements began on 8 June and in Nagqu two days later. The expedition was scheduled so that it would catch the transition between the winter-monsoon regime and summer-monsoon regime, which, on the average, is expected in Lhasa around the 10th of June. Well, we should not have worried, because this year the monsoonal anticyclone was not yet established by 5 July, when the last of our United States team left Lhasa. It was there by 12 July when the se- nior author had a chance to inspect a set of weather maps in southern China. We began to wonder whether the planning of our expedition was the cause for the monsoon delay. The worst delay of recent memory, according to our Tibetan hosts, occurred in 1983 when the plateau monsoon did not come until the end of July. Automatic data recording was maintained, fortunately, past the departure of the United States team. Thus, we anticipate that the monsoon transition period will be recorded on data tapes, which we have been promised to receive. As a consequence of the delayed monsoon, central and western Tibet suffered from a drought. The precipitation events, rather frequent at Nagqu, but rare in Lhasa, were as- sociated with trough extensions embedded in a westerly flow aloft, whereas typical summer-monsoon conditions call for a heat low in the planetary boundary layer and an anticyclonic system in the middle and upper troposphere. Each station carried the following complement of equip- ment: A. Radiation Station. 1) Radiometer pairs (for up ward-flux measurements and downward-flux measurements); Two Eppley precision spectral pyranometers with quartz (W6-295) inner and outer hemispheres for 0.2 jum to 4.0 jum radiation (+/ — 1%); Two Eppley precision spectral pyranometers with col- ored glass (R68-Schott) outer hemispheres for moni- toring 0.7 to 4.0 micrometer radiation (+/— 1%); Two Eppley precision radiometers with silicon hemi- spheres and sink-dome thermistor calibration for 2.0 /jim to 50.0 jum terrestrial radiation (+/— 1%). 2) Campbell Scientific (CSI) cup anemometer and wind

FIG. 3. Erecting the micrometeorological tower at Nagqu.

Unauthenticated | Downloaded 10/03/21 08:06 PM UTC 610 Vol. 68, No. 6, June 1987 vane (model 014A and 024A) for wind speed and direc- concerns will be addressed during the forthcoming data- tion at 3-m above surface (+/— 0.25 m* s-1, +/— 5°). analysis phase of our project: a) What is the variability of 3) CSI 207 thermistor and hygristor at 3 m (+/- 0.2°C, surface-energy budgets and fluxes dependence on synoptic 5% RH). condition and location? b) How representative are the two 4) Six CSI soil thermistors at 0.01, 0.02, 0.05, 0.10, 0.20, measurement sites in terms of regional climates? c) Can our and 0.40 m below surface for soil-temperature mea- observed surface-radiation budgets be used to establish surements (+/- 0.2°C). ground truth for satellite observations? d) How do our mea- 5) Six CSI CEL-WDF-7 ceramic soil-moisture probes at surements compare to others taken in similar and dissimilar the same depth level as the temperature probes. environments? e) Can our measurement results be parame- 6) CSI tipping rain gauge (0.1-mm sensitivity). terized to benefit numerical-model applications? 7) CSI CR-7 data logger to compute 15-min average The question of data representativeness is one that obfus- values from 5-s scan intervals and to record maxi- cates many field-measurement programs, notably those car- mum and minimum values and average data on ried out in complex terrain. The downward-pointing radiom- magnetic tape. (Some data loss occurred at Nagqu eters "see" within their cone of sensitivity only a rather-small because of a sensor-excitation board that had shaken surface area that we chose to carry "typical" vegetation. loose during the kamikaze ride from Lhasa). However, the radiative characteristics of a vegetated surface have to be presumed variable, even if no drastic changes ap- B. Micrometeorological tower station. pear to the naked eye. The Nagqu site showed rather uniform 1) R. M. Young 27005J-Gill u-v-w propeller anemome- and time-invariant ground-cover characteristics. Effects of ters at 5, 10, and 20 m. (Accuracy varies with angle varying density of grass or lichens were monitored frequently of attack, cosine corrections required). with hand-held infrared Teletemp thermometers. On sunny 2) CSI 207 thermistors and hygristors at 0.1, 5, 10, and days these dark-colored lichen crusts were often 10°C to 2Q m (+/- 2°C, +/- 5% RH). 15°C warmer than nearby patches of grass, thus can be 3) CSI CR-7 data logger to compute 5-min-average deemed to contribute significantly to the local surface-energy values, correlation statistics, variances, etc. from 2- budget. Underneath the radiation "monitors," grass pre- s-scan-interval data and to record all parameters on vailed over lichens with an approximate ratio of 7:3. magnetic tape. (The bumpy road conditions between At Lhasa a tribe of voles invaded the area around our ra- Lhasa and Nagqu caused the data logger at Nagqu to diometers and had to be discouraged by pouring kerosene malfunction. Data had to be dumped from computer down their burrows. The damaged surface area was small memory by manual interrogation and had to be enough to be of negligible consequence to our data. The vi- hand-copied). cinity of that site included open water, marsh grass, bare soil, C. NCAR-ADAS radiosonde system with theodolite track- willow trees, and a wheat field, whose surface-temperature ing of balloons. (There also was a major data loss at characteristics were also monitored with an infrared ther- Nagqu due to computer-hardware damage incurred dur- mometer. In addition, team members climbed the south-and ing transit). north-facing mountain sited near Lhasa (the latter after ford- ing the Lhasa River in a yak-skin boat) to obtain surface D. At the Lhasa station atmospheric-turbidity measure- "skin" temperature readings by infrared thermometry of ments were carried out with a University of Arizona typical surfaces under varying sun angles. The highest Solar Photometer measuring in 10 wave-length bands temperatures (in excess of 60°C) were encountered over sand centered at 0.3703,0.3996,0.4409,0.5196,0.6105,0.6703, dunes. 0.7790, 0.8703, 0.9385, and 1.0291 Typical data output for the period 22-28 June at Nagqu E. Teletemp portable infrared thermometers were used to and Lhasa is shown in Fig. 4. Plotted are diurnal cycles of survey local variations of the surface "skin" tempera- downward fluxes and upward fluxes of shortwave (V), near- tures in the vicinity of each measurement site and to ob- infrared radiation (N), their sum (K), and longwave atmos- tain typical readings along mountain slopes during pheric and terrestrial radiation (L). Peak values of K at both climbing excursions. sites can excede 1100 W • m~2 and at Nagqu surpassed those observed by Smith (1986a) on clear days in the Saudi Ara- bian "Empty Quarter" by about 10 percent. Values of close to 1300 W • m~2 at Nagqu are caused by direct transmission 3. Preliminary data sample through the highly transmissive (thin) atmosphere with an additional scattering source from cumulus clouds. The bal- According to an agreement between the National Science ances between incoming and outgoing fluxes in the solar Foundation and the State Meteorological Administration, shortwave and near-infrared spectral regions (K*), in the the data collected in the field will be transferred to 9-track longwave-radiation bands (L*), and the sum of the two are "computer tape" to be analyzed by the United States team depicted in Fig. 5. In these diagrams we have subscribed to and the Chinese team. Copies of the data tapes will also be the convention of plotting fluxes received by the soil surface placed in the public domain at NCAR. The field data will be as negative quantities, and fluxes emitted by the soil as posi- augmented by regional radiosonde and satellite data. Initial- tive quantities. The high values of L* at Nagqu during the analysis efforts will follow procedures outlined by Chen et al. first three days (22-24 June) of the sample shown here are (1985), Smith (1986 a,b), Smith and Reiter (1986), Smith due to a very warm soil surface and a thin, cold, and dry at- et al. (1986) and Sheaffer and Reiter (1987). The following mosphere. These values which excede 300 wm~2 on days Unauthenticated | Downloaded 10/03/21 08:06 PM UTC Bulletin American Meteorological Society 611

FIG. 4. Time series from 22 to 28 June 1986, at a) Nagqu and b) Lhasa of: Vi, the downward visible solar radiation, Ni, the downward near-infrared solar radiation, Ki = Nl + VI, the total downward solar radiation; Vt, the reflected (upward) visible radiation, Nt, the upward near-infrared radiation, Kt = Nt + Vt, the upward total radiation in the solar spectrum region; LI, the downward long-wave (atmospheric) radiation; Lt, the upward long-wave (terrestrial) radiation.

FIG. 5. Time series at a) Nagqu and b) Lhasa for same period as in Fig. 1 of net solar (K*)and net total radiation (Q*), the latter comprised of the solar and long-wave radiation budgets.

FIG. 6. Time series at a) Nagqu and b) Lhasa of sensible heat (HS) and latent heat (HL) for the same time period as in Fig. 1.

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FIG. 7. Time series at a) Nagqu and b) Lhasa of air temperature (Ta) and relative (RH) measured 3-m above ground.

172-173 are higher than the peak values observed by Smith regimes at Nagqu are revealed not only in the relative-humid- (1986a) in the Arabian desert in June by 10 to 20 percent. The ity regimes, but also in the amplitudes of the diurnal temper- arrival of clouds and moisture after the 24th damps the radia- ature cycles. Nighttime air temperatures close to the ground tive heat loss quite effectively. The disruption of the fluxes in can drop to below freezing even in summer. This is why Tibe- the afternoon of Julian Day No. 173 at Lhasa was caused by tan herdsmen never mothball their sheepskin coats. On an intense convective squall that broke abruptly from a rela- warm days they still wear them below their waists, held up by tively warm and clear day and kicked up a veritable dust a belt, and over one arm, thus allowing half of the coat to storm in and around Lhasa. (Reiter's notes: "A heavy wind, become a giant receptacle for odds and ends needed in the dust, rain and thunderstorm in the afternoon [blowing dust field. Of course, this furry climate-control device also exudes along the mountain sides lets us appreciate the origin of the a characteristic fragrance of yak-dung fire, yak-butter can- many sand dunes] looks more like the passage of an upper dles, and perspiration, which all of us will forever associate trough than the action of the monsoon"). Even though with the magnificent and mystic ambience of Tibetan tem- hardly any precipitation reached the bottom of Lhasa valley ples and shrines. during such squalls, mountain tops surrounding the valley Mean diurnal cycles of radiation fluxes for the seven-day became temporarily blanketed with hail and snow. period at Nagqu and for the first three "dry" days are shown Preliminary estimates of the sensible-heat fluxes (Hs) and in Figs. 8a and 8b, and for the seven-day period at Lhasa in latent-heat fluxes (Hi) derived at the radiation stations with Fig. 8c. During the "dry" period at Nagqu the downward the aid of a bulk aerodynamic-computation scheme (Sheaffer surface solar fluxes are significantly higher than during the and Reiter, 1987) are given in Fig. 6. The values shown here cloudy and wet period. Ultimately this is how the plateau compare favorably with Bowen ratios computed from the monsoon shuts off the elevated heat source. micrometeorological-tower station data. The first three days Daily mean values of these fluxes are summarized in Table in the sample given for Nagqu were dry and, consequently, 1, together with their seven-day averages. Notably, the values showed a prevalence of Hs, whereas the remaining four days, of Ht given here are slightly larger than those derived by after a frontal rain squall on 25 June, had precipitation (1.5 Chen et al. (1985) from precipitation data, are similar to cm on the 25th), shifting the burden of total heat flux into the those estimated by Luo and Yanai (1984), but fall signifi- atmosphere to Hi. Even during the dry days one has to make cantly short of the values reported by Yeh and Gao (1979). allowances for evapotranspiration from the short and sparse Albedos for the shortwave (AV), near-infrared (AN) and grass, because its root system extends to more than 40 cm total solar-radiation bands (Ak) are shown in Fig. 9, together where the soil moisture is near "field capacity." (A hand-ex- with the equivalent black-body temperatures of soil (out- cavated well about 0.5 km from the Nagqu site showed the going arrow) and atmosphere (incoming arrow). The asym- water table to be at least 10 m from the surface.) At the Lhasa metry in the AN curve for clear days at Nagqu (Fig. 9b) has to site the high ground-water table next to a lagoon with stag- be attributed mainly to the slight terrain slope towards the nant water and denser vegetation caused Hi to prevail west. The asymmetry reverses its shape when cloudy days are throughout the sample period. Moisture from the warm and included in the sample (Fig. 6a) because of the afternoon wet subsoil moved upward during the night and condensed at prevalence of diffuse radiation over direct radiation. At the surface, causing "wet" patches to appear even on barren Lhasa the asymmetry can also be ascribed to different terrain soil areas in the absence of any measurable precipitation. and ground cover characteristics to the east and west of the Such conditions, while encountered in the river valley, are station (see Fig. 2).6 not characteristic for the dry and barren mountain sides which, in the Lhasa region, are partly covered by sand dunes. Time series of air temperatures (Ta) and relative humidi- 6 Most of the morning and evening "spikes" in AN will have to be ties (RH) are shown in Fig. 7. The "dry" and "wet" synoptic attributed to instrument characteristics at low sun angles.

Unauthenticated | Downloaded 10/03/21 08:06 PM UTC Bulletin American Meteorological Society 613 Finally, in Fig. 10 an attempt is made to summarize the di- urnal cycles of the energy budget components 1) HG + HT - Q* = 0 and 2) HT — HL H~ Hs, where HG is the heat storage in the ground derived from the soil thermometers, and Q* the total solar and terrestrial radiation budget, com- prised of K* and L*. Again, the relative importance of HL becomes evident, somewhat exaggerated by the moist river valley near Lhasa, but still surprisingly large at Nagqu if one

FIG . 8. Mean diurnal variations at a) Nagqu averaged for the pe- riods 22 to 28 June 1986 and b) 22 to 24 June ("dry" period), and at c) Lhasa for the period 22 to 28 June, for the following parameters: VI, the downward visible solar radiation, Ni, the downward near- infrared solar radiation, Ki = VI + Ni, the total downward solar radiation; Vt, the reflected (upward) visible solar radiation, Nt, the FIG. 9. Mean diurnal variations for same locations and periods reflected near-infrared radiation; Kt = Vt + Nt, the total reflected as in Fig. 8, but for atmospheric (EBBT1) and surface equivalent solar radiation; Lt = downward (atmospheric) long-wave radia- black-body temperatures (EBBTt), and for visible (Av), near-in- tion; Lt = emitted (terrestrial) long-wave radiation. frared (AN) and total albedo (AK) of solar radiation.

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TABLE 1. Daily and seven-day averages of surface-energy budget components (w • m 2) for the period June 22 to 28, 1986, at Nagqu and Lhasa, Tibet (Xizang Autonomous Region). Daily Average Seven-day Date Average Site/ Parameters 22 23 24 25 26 27 28 Nagqu Q* -147 -135 -149 -49 -76 -168 -213 -131 HT 126 112 120 56 79 141 174 115 HL 13 12 13 71 82 127 137 65 Hs 113 100 107 -15 -3 14 37 50 Ho 21 23 29 -7 -3 27 39 16 Lhasa Q* -154 -125 -132 -126 -160 -108 -157 -137 HT 142 124 134 129 153 115 145 134 HL 124 123 135 127 150 115 146 131 Hs 18 1 -1 2 3 0 -1 3 Hg 12 1 -2 -3 7 -7 12 3 allows for the fact that the "monsoonal" rainy season had not yet started during the sample period for which data have been presented here. Thus of major focus in our measure- ments and of critical importance in understanding plateau monsoon behavior, is the role of soil moisture and latent- heat exchange. The historical view suggests that central Tibet lacks a sufficient ground moisture source for heating and moistening the atmosphere. Our recent measurements tend to dispel that notion.

4. Outlook A great deal more data-analysis work lies ahead, especially when synoptic conditions, radiosonde, and satellite informa- tion can be integrated with the field data collected at the two Tibetan sites. Our preliminary data checks and analyses sat- isfied us to the extent that, allowing for a few instrument fail- ures, our data base is not a collection of colorful or random errors. Was TIPMEX-86 worth the effort? By any standards, the expedition was an adventure that none of us will ever forget. The challenges offered by nature, logistics, and bureaucracy were met head-on. The wealth of experience gained by our team members should benefit future enterprises. The data re- trieved from the two sites are unique and will provide grounds for many interesting comparisons. The Chinese team, just as much cast into a strange environment as the United States team, quickly absorbed the new measurement technologies in spite of the language barrier. That barrier sometimes gave rise to a bit of confusion, as evident from the following dialogue between Reiter (who wanted to take solar- photometer measurements from the roof of the hotel build- ing) and a waitress at the Tibet Guesthouse in Lhasa who had been introduced as being fluent in English: Reiter: "Is it possible to go out on the roof tomorrow morning?" FIG. 10. Mean diurnal variations at a) Nagqu and b) Lhasa for Waitress (smiling): "Yes". the period 22 to 28 June 1986 of the following surface energy budget Reiter: "Is the roof flat?" parameters: Q* = total net radiation, Hs = sensible heat flux to Waitress (pointing at a serving tray and smiling): "Like atmosphere, HL = latent heat flux to atmosphere, HT = total heat this" flux to atmosphere, Ho = heat flux into ground.

Unauthenticated | Downloaded 10/03/21 08:06 PM UTC Bulletin American Meteorological Society 615 Reiter: "Yes. Can I go to the roof tomorrow morning?" early summer of 1979. Part II: Heat and moisture budgets. Mon. Waitress (smiling): "How many persons?" Wea. Rev., 112, 966-989. Reiter: "Two". Reiter, Elmar R., and Gabriella J. Reiter, 1981: Tibet—The last Waitress (smiling): "Chinese breakfast or western break- frontier. Bull. Amer. Meteor. Soc., 62, 4-13. Sheaffer, John D., and Elmar R. Reiter, 1987: Measurements of sur- fast?" face energy budgets in the Rocky Mountains of Colorado. J. Geoph. Res., 91. Smith, Eric A., 1986a: The structure of the Arabian heat low. Part I: Acknowledgments. The project described here was supported by Surface energy budget. Mon. Wea. Rev., 114, 1067-1083. NSF Grants ATM 83-13270 and ATM 84-17878 and U.S. Air Force Smith, Eric A., 1986b: The structure of the Arabian heat low. Part II: Grant AFSOR F49620-86-6-0080. Bulk tropospheric heat budget and implications. Mon. Wea. Rev., 114, 1084-1102. Smith, Eric A., and Elmar R. Reiter, 1986: Monitoring the spring- summer surface energy budget transition in the Gobi Desert using AVHRR GAC data. Preprint Volume of 2nd AMS Conference on References Satellite Meteorology/Remote Sensing and Application, 12-16 May 1986, 286-290. Chen, Longxun, Elmar R. Reiter, and Zhiqiang Feng, 1985: The at- Smith, Eric A., Elmar R. Reiter, and Youxi Gao, 1987: Transition of mospheric heat source over the : May-August the surface energy budget in the Gobi Desert between spring and 1979. Mon. Wea. Rev., 113, 1771-1790. summer seasons. J. Climate Appl. Meteor., 26. Luo, R. H., and M. Yanai, 1984: The large-scale circulation and heat Yeh, T. C., and Y. X. Gao, 1979: The meteorology of the - source over the Tibetan Plateau and surrounding areas during the Xizang Plateau. Science Press, Beijing, 278 pp. (in Chinese). •

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