The Food and Agriculture Organization (FAO) has proposed the FAO 56 Penman-Monteith model as a standard method for estimating reference evapotranspiration (ETo). However, using this model for the high-altitude regions mostly faces uncertainty due to the lack of meteorological stations, observation problems, and incomplete meteorological data. Therefore, in these regions models should be used that require fewer meteorological variables and can also be considered as a function of altitude. In the present study, the data from 28 synoptic stations in Iran with an altitude of more than 2000 meters above sea level in the period of 1989-2019 were used to modify the Hargreaves-Samani model based on the altitude and also correct the temperature factor coefficients. The comparison of the results of the FAO 56 Penman-Monteith model as a standard method, the original Hargreaves-Samani, and the modified Hargreaves-Samani models showed that the modified model offers better results than the original model and is able to estimate the ETo more accurately in the highaltitude regions of Iran. Based on the results of MBE, MAE, RMSE, PVC, LVC, d, r, and PI statistical indices, the highest agreement in estimating ETo with modified Hargreaves-Samani and FAO 56 Penman-Monteith models was observed at Firuzkuh, Baft, Baladeh, Sisakht, Avaj, Khansar, Abali, Daran, Fereidunshahr, Borujen, Samirom, Aligudarz, Farokhshahr, Damavand, Sepidan and Saman stations, which had an average error reduction of 14% compared to the values obtained from the original Hargreaves-Samani model.

In this paper, it is tried to design an altitude hold mode autopilot of unmanned aerial vehicles (UAV's).This autopilot has practical importance for VAV's due to flying in the vicinity of terrain to implement missions by terrain following maneuvers. This case presents an interesting challenge due to the non-minimal phase characteristics, non-linearities, and uncertainties of altitude to elevator relation. Unlike the conventional methods (in which the altitude autopilot is designed with three loops, so that altitude, pitch rate, and pitch angle variables are measured), a single loop scheme is proposed so that only altitude is measured. This single loop scheme is simple, but it is not robust with respect to the uncertainties. The fuzzy logic control is proposed to overcome parametric uncertainties and unmodeled dynamics (due to the complexity and expenses in aerospace industries, these uncertainties are usually available in modeling).Our 6DOF non-linear simulation shows that it is possible to achieve a simple and robust autopilot by fuzzy logic control.

In this study, MODIS daily snow products (MOD10A1 and MYD10A1) were used in the period 2003-2020, and the snow line height in the northwestern territory of Iran (in two ways: 1) the 0˚ isotherm using LST data and 2) for each cell where there is both snow cover and LST is 0˚ or below 0˚) was estimated monthly, seasonally, annually and long-term, and area maps were drawn. Based on the first and second algorithms, the snow line height was in the maximum phase in January and in the minimum phase in July and August. Based on the second algorithm, in January, negative temperature anomalies accompanied by snowfall led to the expansion of the snow line to an altitude of 1974 meters. The increase in air temperature, snow melting and the sharp decrease in snow cover in July and August have caused the regression of this phenological snow characteristic to an altitude of 4811 meters (Sablan Mountain). In the second algorithm, the maximum advance of the snow line height from October to November by 1374 meters towards lower altitude classes has occurred. The snow line height in the winter season (maximum phase) has been moved to an altitude of 2230 meters based on the second algorithm and to an altitude of 4805 meters in the summer pattern (minimum phase). According to the second algorithm, the years 2011 and 2010 have the lowest and highest snow line heights with an altitude of 3408 meters and 3692 meters, respectively.

Dear Editor, The progressive exposure to an increasing altitude results in a series of adjustments of various organs and systems (i. e., acclimatization) in healthy subjects; this requires them to stay on the mountain for longer or shorter periods. Knowledge about the cardiovascular adaptations to altitude in healthy subjects and known cardiac patients is very important when it comes to recommending appropriate preventive strategies and to assess the risk of adverse events specific to the mountains (“ mountain sickness” ) or pre-existing heart disease. To date, no guidelines concerning cardiac patients and high altitude are available. ...