Abstract
The present study presents a detailed analysis of the diurnal and monthly cycles the surface boundary layer and of surface energy balance in a sparse natural vegetation canopy on Huancayo observatory (12.04 ∘ S, 75.32 ∘ W, 3313 m ASL), which is located in the central Andes of Perú (Mantaro Valley) during an entire year (May 2018–April 2019). We used a set of meteorological sensors (temperature, relative humidity, wind) installed in a gradient tower 30 m high, a set of radiative sensors to measure all irradiance components, and a set of tensiometers and heat flux plate to measure soil moisture, soil temperatures and soil heat flux. To estimate turbulent energy fluxes (sensible and latent), two flux–gradient methods: the aerodynamic method and the Bowen-ratio energy-balance method were used. The ground heat flux at surface was estimated using a molecular heat transfer equation. The results show minimum mean monthly temperatures and more stable conditions were observed in June and July before sunrise, while maximum mean monthly temperatures in October and November and more unstable conditions in February and March. From May to August inverted water vapor profiles near the surface were observed (more intense in July) at night hours, which indicate a transfer of water vapor as dewfall on the surface. The patterns of wind direction indicate well-defined mountain–valley circulation from south-east to south-west especially in fall–winter months (April–August). The maximum mean monthly sensible heat fluxes were found in June and September while minimum in February and March. Maximum mean monthly latent heat fluxes were found in February and March while minimum in June and July. The surface albedo and the Bowen ratio indicate semi-arid conditions in wet summer months and extreme arid conditions in dry winter months. The comparisons between sensible heat flux ( Q H ) and latent heat flux ( Q E ), estimated by the two methods show a good agreement (R 2 above 0.8). The comparison between available energy and the sum of Q E and Q H fluxes shows a good level of agreement (R 2 = 0.86) with important imbalance contributions after sunrise and around noon, probably by advection processes generated by heterogeneities on the surface around the Huancayo observatory and intensified by the mountain–valley circulation.
Highlights
The lower natural boundary of the atmosphere is the earth’s surface
Transport processes of mass and energy between the atmosphere and the earth’s surface modify the lowest part of the atmosphere, creating the planetary boundary layer (PBL) [1], which plays an important role in many fields, including weather forecasting and climate, mesoscale meteorology, hydrology, agricultural meteorology, and air pollution [2]
The present contribution tries to partially cover the lack of information of the seasonal and diurnal cycles of the surface boundary layer and of the energy-balance components in the Huancayo observatory located in central Andes of Perú using a set of sensors to measure temperature, relative humidity, and wind at different heights
Summary
The lower natural boundary of the atmosphere is the earth’s surface. Transport processes of mass and energy between the atmosphere and the earth’s surface modify the lowest part of the atmosphere, creating the planetary boundary layer (PBL) [1], which plays an important role in many fields, including weather forecasting and climate, mesoscale meteorology, hydrology, agricultural meteorology, and air pollution [2]. The results show the schemes that generated the most rainfall were those of a more unstable boundary layer with weaker wind speeds, at least with easterly winds Motivated by these considerations, the present contribution tries to partially cover the lack of information of the seasonal and diurnal cycles of the surface boundary layer and of the energy-balance components in the Huancayo observatory located in central Andes of Perú using a set of sensors to measure temperature, relative humidity, and wind at different heights. The main results and discussions about the seasonal and diurnal cycle behavior the surface boundary layer and of the energy-balance components along the year are presented in Sections 4 and 5.
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