The CNR 4 net radiometer hes been installed in Lukla in 2013 and it consists of a pyranometer pair, one facing upward, the other facing downward, and a pyrgeometer pair in a similar configuration. The pyranometer pair measures the short-wave radiation. And the pyrgeometer pair measures long-wave radiation. The upper long-wave detector of CNR 4 has a meniscus dome. This ensures that water droplets role off easily and improves the field of view to nearly 180°, compared with a 150° for a flat window. All 4 sensors are integrated directly into the instrument body, instead of separate modules mounted onto the housing. But are each calibrated individually for optimal accuracy. Two temperature sensors, a Pt-100 and Thermistor, are integrated for compatibility with every data logger. The temperature sensor is used to provide information to correct the infrared readings for the temperature of the instrument housing. Care has been taken to place the long-wave sensors close to each other and close to the temperature sensors. This assures that the temperatures of the measurement surfaces are the same and accurately known. Which improves the quality of the long-wave measurements. Technical Characteristics: Spectral range: 300 to 2800 (short wave) nm Spectral range: 4500 to 42000 (long wave) nm Sensitivity: 5 to 20 µV/W/m² Temperature dependence of sensitivity (-10 ºC to +40 ºC) : < 4 % Response time: < 18 s Non-linearity: < 1 % Operating temperature: -40 to 80 °C Ventilation power (of the optional CNF 4 ventilation unit): 10 W

Since 2013, the Digital Barometer PTB330, by VAISALA, is installed in Lukla. Vaisala BAROCAP® Digital Barometer PTB330 is a new generation barometer, designed for a wide range of high-end atmospheric pressure measurement. -Vaisala BAROCAP® sensor -Accurate measurement -Excellent long-term stability -Added reliability through redundancy -Graphical trend display with 1-year history data -Altitude corrected pressure (QFE, QNH) -For professional use in meteorology, aviation, laboratories, and demanding industrial applications

In Lukla the CX115P Lsi-Lastem barometer is connected with a measurement system (recorder, data logger) that accepts analog signals. The barometer works according to the piezometric principle: a resistive film is deposited on a slice of silica with a bridge form; as the pressure changes, the slice will deform and consequently changes the system's resistance. The CX115P model mounts a special thermal compensation system that significantly reduces drift. General characteristics: Range: 800 ž 1100 hPa (1 hPa=1 mBar) Sea level correction range: -300...+2000 mt. Thermal drift: 0,01 hPa/°C (-10..+60°C) Linearity&Hysteresis: < 0,3% of the range Overload: max. 2 Pa Load resi stance: Current output types: <500W. Power consumption: 3 W Response time (T90): 1 ms Environmental limits: -25 .. +60°C Output connections: terminals Weight: 650 gr. Housing case material: Plastic Protection: IP40 Downward cable outlet

At the Lukla station the the CM6B pyranometer, manufactured by Kipp & Zonen is installed. This sensor is a first class pyranometer as defined by the World Meteorological Organization. It is suitable for the measurement of solar irradiance on a plane surface (W/m2). It incorporates a 64-thermocouple sensor, which is rotationally symmetrical, housed under K5 domes. A white screen prevents the body of the pyranometer from heating up. The pyranometer is supplied with a spirit level and screws for accurate levelling. CM6B technical data - Spectral range 305 to 2800 nm (50%points) - Sensitivity 9 to 15 ?V/Wm-2 - Impedance 70 to 100 Ohm - Response time 1/e 5 s, 99 % 55 s - Non-linearity <1.5 % (<1000 W/m 2 ) - Tilt error <1.5 % at 1000 W/m 2 - Operating temperature -40 to +90 °C - Temperature dependence of sensitivity _2 % (-10 to +40 °C) - Maximum irradiance 2000 W/m2 - Directional error < _20 W/m2 at 1000 W/m2 - Weight 0.85 kg - Cable length 10 m

In 2013 the Wind Set WA15 by Vaisala has been installed in Lukla. Overview • High-performance wind measurement set • Long and successful track record in meteorological applications • Low measurement starting threshold • Conical anemometer cups provide excellent linearity • Heated shaft prevents bearings from freezing Technical Specifications Wind speed Sensor / transducer type: cup anemometer / opto-chopper Measurement range: 0.4...75 m/s Starting threshold: <0.5 m/s * Distance constant: 2.0 m Accuracy (range 0.4...60 m/s) with characteristic transfer function: ±0.17 m/s ** with transfer function U=0.1xR: ±0.5 m/s Wind direction Sensor / transducer type: vane / optical code disc Measurement range: 0...360° Starting threshold: <0.4 m/s Delay distance: 0.4 m Resolution: ±2.8° Accuracy: better than ±3°

At the AWS Lukla station the DQA035 Lsi-Lastem rain gauge is mounted on a 1,5 m pole. This model of Rain gauge has a 1.000 cmq collector area. The measurement device is composed of a collector cone and a double chamber bascule connected to a magnete that operates one (optional two) reed switch, which generates impulses that can be counted by external meters: each impulse is equal to 0.2 mm of rain (optional from 0.1 to 0.5 mm). The mechanical and electrical specifications are: - Collector surface area: 1000 cmq - Collector area diameter: 420 mm - Measurements range: 180 mm/hr - Resolution: o,2 mm/imp. (opt. 0,1; 0,3; 0,4; 0,5; mm/imp.) - Accuracy: 0-1 mm/min: 1%; 1-3 mm/min: 2%; 3-5 mm/min: 4%; 5-10 mm/min: 8% - Contact: 1 reed (opt. N.2 reed) 0,5 A/24V non inductive - Pulse duration: 100 msec.± 5 - Collector cone material: Brass - External housing material: Inox AISI30 - Tipping bucket material: Alluminium - Cable: 10 m - Weight: 6,3 kg - Power supply: /thermocover 100 W, 24 Vca/Va

The oxygen saturation values reported in the high altitude literature are usually taken during a few minutes of measurement either at rest or during exercise. We aimed to investigate the daily hypoxic profile by monitoring oxygen saturation for 24h in 8 lowlanders (4 females, ages 26 to 59) during trekking from Lukla (2850m) to the Pyramid Laboratory (5050m). Oxygen saturation was measured (1) daily at each altitude (sm), (2) for 24-h during ascent to 3500m, 4200m, and on day 1 at 5050m (lm), and (3) during a standardized exercise (em). Results: (1) the sm and lm values were 90.9% (±0.5) and 86.4% (±1.1) at 3500m; 85.2%(±1.1), and 80% (±1.9) at 4200m; 83.8%(±1) and 77% (±1.7) at 5050m (p<0.05); (2) the daily time spent with oxygen saturation <90% was 56.5% at 3500m, 81% at 4200m, and 95.5% at 5050m; (3) during exercise, oxygen saturation decreased by 10.58%, 13.43%, and 11.24% at 3500, 4200, and 5050?m, respectively. In conclusion, our data show that the level of hypoxemia during trekking at altitude is more severe than expected on the basis of a short evaluation at rest and should be taken into account.

The HMS 9000, developed by SDEC, France, is a soil moisture sensor for the measurement of water content in soil, based on the principle of the electrical capacity measurement.

Reliable measurements of snow-depth in extreme conditions using a USH-8 Ultrasonic Snow Depth Sensor installed to Lukla station.

Measurements intended for the analysis of the radiation balance of Solar and Far Infrared radiation. The most common application is the measurement of Net (total) Radiation at the earth's surface. The CNR1 net radiometer by Kipp & Zonen is for applications requiring research-grade performance. The radiometer measures the energy balance between incoming short-wave and long-wave IR radiation versus surface-reflected short-wave and outgoing long-wave IR radiation.