High Net Radiation Research Articles

Evapotranspiration and energy balance of native wet montane cloud forest in Hawai‘i

Evapotranspiration (ET) and energy balance were observed, using eddy covariance and other micrometeorological measurements, at a native Metrosideros polymorpha forest site in Hawai‘i. Total rainfall for the 12-month study period (2401 mm) was close to the long-term mean (2500 mm year −1), but was highly variable from month to month with distinct dry periods in February, May, and December 2005. Measured annual ET of 996 mm year −1 was slightly higher than previous estimates for similar locations in Hawai‘i. However, the energy closure ratio was 0.784, leading us to adjust turbulent energy fluxes upward by 27.6%. The resulting adjusted annual ET of 1232 mm is significantly higher than previous forest ET estimates for Hawai‘i. Variations in canopy conductivity suggest that midday stomatal closure is occurring and/or that evaporation is high in the morning because of frequent wet canopy conditions early in the day. The daily fraction of turbulent energy flux used for ET was observed to be lower for days with high net radiation, indicating that transpiration is being limited under conditions of high evaporative demand. ET was generally higher during rainy periods than dry periods. After controlling for differences in available energy, ET is, on average, 29% higher on days with rain than days without rain. The fraction of energy used for ET follows a distinct annual pattern, roughly corresponding to the observed cycle in leaf area at the site, with a minimum in mid-April and a maximum in mid-October. Variations in rainfall appear to be the cause of deviations from the annual cycle of the fraction of energy used for ET. This suggests that ET is strongly controlled by variations in canopy wetness at this wet forest site.

Long-term change, interannual and intra-seasonal variability in climate and glacier mass balance in the central Greater Caucasus, Russia

AbstractLong-term trends, interannual and intra-seasonal variability in the mass-balance record from Djankuat glacier, central Greater Caucasus, Russia, are related to local climate change, synoptic and large-scale anomalies in atmospheric circulation. A clear warming signal emerged in the central Greater Caucasus in the early 1990s, leading to a strong increase in ablation. In the absence of a compensating change in winter accumulation, the net mass balance of Djankuat has declined. The highest value of seasonal ablation on record was registered in the summer of 2000. At the beginning of the 21st century these trends reversed. Ablation was below average even in the summer of 2003, which was unusually warm in western Europe. Precipitation and winter accumulation were high, allowing for a partial recovery of net mass balance. The interannual variability in the components of mass balance is weakly related to the North Atlantic Oscillation (NAO) and the Scandinavian teleconnection patterns, but there is a clear link with the large-scale circulation anomalies represented by the Rossby pattern. Five synoptic categories have been identified for the ablation season of 2005, revealing a strong separation between components of radiation budget, air temperature and daily melt. Air temperature is the main control over melt. The highest values of daily ablation are related to the strongly positive NAO which forces high net radiation, and to the warm and moist advection from the Black Sea.

Analysis of meteorological data and the surface energy balance of McCall Glacier, Alaska, USA

AbstractWe report on analysis of meteorological data for the period 27 May–20 August 2004, from two automatic weather stations on McCall Glacier, Alaska, USA, aimed at studying the relationship between climate and ablation. One station is located on a mountain ridge and the other in the ablation area where we also analyzed the energy balance. The weather station on the glacier measured an average temperature of 5.3°C (at 2 m height above surface) and wind speed of 3.1 m s−1 (at 3 m height). A sonic height ranger and ablation stakes indicate a specific mass balance of –1.94 ± 0.09 m w.e between 15 June and 20 August. The specific mass balance calculated from the surface energy balance, –2.06 ± 0.18 m w.e., is in close correspondence to this. The latter is the sum of 0.12 m w.e. of snowfall, 0.003 m w.e. of deposition and –2.18 m w.e. of melt. Net radiation contributes 74% of the melt energy. Compared to ablation measurements in the early 1970s, summer ablation was large. This increase is explained by a combination of a relatively higher net radiation, a lower albedo and larger turbulent heat fluxes that led to more energy being available for melting. No single meteorological variable can be isolated as being the principal reason for the high ablation, however. The lower ice albedo (0.19) is possibly due to ash deposits from forest fires.

Thermal Characteristics and Energy Balance of Various-Size Canadian Shield Lakes in the Mackenzie River Basin

This study addresses the thermal and energy budget characteristics of four different-size Canadian Shield lakes in the Mackenzie River basin during the ice-free season of 2000. The objectives are to characterize and compare the surface temperature and thermal structures, and to quantify the magnitudes and flux rates of the energy balance components of each lake. This study highlights the variability in thermal and energy balance characteristics arising from differences in mean lake depth and surface area. The lakes exhibit similar temporal patterns for air temperature, net radiation, wind speed, and wind direction. Net radiation and wind speed are highest over the largest lake, Great Slave Lake, due to colder surface temperatures and lengthy across-lake wind fetch, respectively. During the warming phase of the summer, surface temperature is inversely related to mean depth; however, during the cooling phase this relationship reverses. The shallowest of the four lakes remains isothermal during the entire ice-free period, while the three larger and deeper lakes are all dimictic. A lag in the onset of thermal stratification in the dimictic lakes is positively correlated with mean depth and surface area. Large evaporative water losses correspond to periods of low net radiation and cold dry air over Great Slave Lake. However, over the smaller, shallower lakes periods of high evaporation occur on days with high net radiation and warm, dry air. The capacity of larger lakes to store more heat results in longer ice-free periods and higher evaporation. Maximum heat content increases and occurs later for lakes of greater depth. Maximum evaporative rates occur later and cumulative evaporation is highest for lakes of greater depth and area. The ratios of total open water evaporation for the four lakes in order of size (smallest 5 1.0) are 1.0 : 1.2 : 1.3 : 1.4. Evaporation magnitudes are discussed in the context of other temperate and high-latitude lake studies.

Study of diurnal cycle of convective precipitation over Amazonia using a single column model

The error in the diurnal cycle of precipitation over land in the tropics in the European Centre for Medium‐Range Weather Forecasts forecast model is investigated using a single column model with idealized forcing of the omega field, as well as short‐term and long runs of the full three‐dimensional model. The model precipitates a few hours after sunrise, as it does not represent correctly the morning development of a growing cumulus boundary layer. In the single column model, precipitation is closely linked to the mean forcing and surface evaporation, but the phase of diurnal varying omega forcing in relation to the diurnal solar cycle determines the relation of convective to large‐scale precipitation in the control model, as well as cloudiness and the net radiation balance. With diurnal subsidence peaking at midnight, but no mean ascent, the model shows a quasi 2‐day precipitation mode. With both strong mean ascent and diurnal forcing, ascent peaking in the daytime gave stratiform rain with large cloud cover and very low surface net radiation, while daytime subsidence and ascent at night gave strong daytime convective precipitation and high net radiation.

Surface energy exchanges and interactions with thunderstorms during the Maritime Continent Thunderstorm Experiment (MCTEX)

Inputs of heat and moisture through surface energy exchanges are important in the evolution of diurnally modulated thunderstorms. As part of the Maritime Continent Thunderstorm Experiment (MCTEX) conducted on the Tiwi Islands, northern Australia, we measured the surface energy exchanges above the dominant surface types (savanna, grassland, forest and shallow tidal strait). Measurements were made during the monsoon transition period (October–December) using the Bowen ratio and the aerodynamic techniques. A full radiation balance was measured at the Savanna site, where the surface albedo was determined as 0.19. The surface energy exchanges showed broad similarities between the sites, with comparable high net radiation totals averaging 11.8 MJ.m−2.day−1 over the terrestrial sites. The substrate heat fluxes were large at the Tidal strait (4.21 MJ.m−2.day−1) due to the high rates of energy absorption into water. The partitioning of net radiation into sensible and latent heat fluxes was controlled primarily by surface characteristics such as soil moisture and vegetation cover, with Bowen ratios averaging 1.08, 0.65, 0.5 and 0.40 for grassland, forest, savanna and tidal strait sites, respectively. A higher Bowen ratio was recorded at the Grassland site as this was during an earlier period that was much drier. Strong relationships were observed between the total surface convective fluxes and boundary layer development (e.g., the lifting condensation level) and between the magnitude of the daytime surface sensible heat flux and the onset time of thunderstorm convection. Observed terrestrial surface fluxes of moisture (averaging 165–265 W.m−2) were deemed insufficient for observed thunderstorm initiation and suggest that sea breeze advection of moisture is necessary. Tiwi Island thunderstorms were shown to represent a dynamic system where surface fluxes are important in generating a boundary layer sufficient to initiate the thunderstorms but where feedbacks between thunderstorms and surface fluxes eventually help terminate the storms.

Near‐surface climate in the boreal forest

This paper addresses processes that affect near‐surface climate over the boreal forest, using data from the Boreal Ecosystem‐Atmosphere Study (BOREAS) northern study area just west of Thompson, Manitoba. The boreal forest is marked by a very large seasonal cycle with below‐freezing temperatures for half the year. The freezing and thawing of the soil plays an important role in the climate at high latitudes. It moderates winter temperatures (together with the insulating snow cover), because during the freeze process, the effective heat capacity of the soil is greatly increased, and it introduces a significant lag into the climate system. Perhaps the most important consequence is that water is unavailable for evaporation and photosynthesis until snow melts and the ground thaws, which occurs late in spring. As a result, in April and in early May, relative humidity (RH) is a minimum, the surface sensible heat flux is large, and the daytime boundary layer (BL) is very deep, because of this unavailability of water. The situation reverses in the fall, when the ground is warmer than the cooling atmosphere, and mean RH is high and BL depths low. This asymmetry between spring and fall can be seen in both seasonal and diurnal cycles. The forest is heterogeneous, and there is a marked difference in summer in daytime evaporative fraction between the conifers and the deciduous forest and fens. However, above the forest the daytime BL has a strong homogenizing effect, and it is the dominant coniferous forest that controls the mean BL depth. The impact of recent rainfall, stored on the canopy, in the surface moss layer, and in the top soil layer can be readily seen in summer. BL depths rise on succeeding days without rain. A comparison of the fen and young jack pine sites shows the important role of the stomatal control by conifers on transpiration. Since evaporation goes down at high net radiation and low RH for conifer sites, it is clear that the low RH and high BL depth over the forest are a direct consequence of stomatal control. At night, however, temperature, relative humidity, and CO2 are quite heterogeneous under the stable BL. We show that uncoupling of the stable BL at night inside the forest canopy occurs at low wind speeds and high outgoing net radiation and can lead to a 5K cooling within the canopy.

The influence of subtropical cold fronts on the surface energy balance of a semi-arid site

The passage of subtropical cold fronts through central Australia produces the only significant mesoscale meteorological features in the region. The interaction of these cold fronts with the surface energy balance strongly affects the local weather and climate. The surface energy balance was measured at a semi-arid site in Alice Springs, central Australia, to determine how it was influenced by the passage of subtropical cold fronts. Both Bowen ratio and eddy correlation methods were used. The daytime energy balance of the site showed high net radiation that was partitioned into 75% sensible heat flux and 25% soil heat flux with little or no latent heat flux. At night there was a large net radiative loss that was balanced primarily by a loss of heat from the soil. The cold fronts predominately passed through Alice Springs at night and showed a strong surface signature. The fronts brought moister air resulting in higher water vapour pressures during their passage. The nocturnal boundary layer was often disturbed as the front passed, resulting in warm, moist air being mixed down toward the land surface. Mixing decreased the soil heat flux and increased latent heat fluxes toward the surface. Moisture that accumulated at the surface at these times was often evaporated after a return to drier conditions. During the daytime, surface signatures in soil and sensible heat fluxes were less distinct due to the strong convective mixing. Latent heat fluxes followed a similar trend to the nocturnal case.

Comparison of the NCAR LSM1 land surface model with BOREAS aspen and jack pine tower fluxes

Tower fluxes measured at the Boreal Ecosystem‐Atmosphere Study southern study area old aspen (SSA‐OA), southern study area old jack pine (SSA‐OJP), and northern study area old jack pine (NSA‐OJP) sites during the three 1994 intensive field campaigns (IFCs) (May 24 to June 16 (IFC‐1), July 19 to August 10 (IFC‐2), and August 30 to September 19 (IFC‐3)) were compared to fluxes simulated by a land surface model for the same period. Comparisons were limited to the average diurnal cycle for these periods to mitigate large day‐to‐day variability in the observations and problems with missing data. For consistency with the global implementation of the model, vegetation and soil parameters were not set to site‐specific values but rather were the generic needleleaf evergreen and broadleaf deciduous vegetation and the generic sandy and loamy soil used in the global model. Despite the use of generic vegetation and soil, the model reasonably simulated the diurnal cycle of sensible heat, latent heat, net radiation, and CO2 fluxes for the SSA‐OJP and SSA‐OA sites. The main errors were that the model did not reproduce the midday reduction in latent heat seen at the SSA‐OJP site during IFC‐1 and IFC‐2 and had less photosynthetic CO2 uptake than observed at the SSA‐OA site. Differences in vegetation structure and physiology between the two sites were important to accurately simulate the fluxes. The needleleaf evergreen vegetation resulted in higher net radiation and a higher Bowen ratio than the broadleaf deciduous vegetation. Soil differences were less important. The NSA‐OJP site was not so well simulated: midday latent heat flux was overestimated, and photosynthetic CO2 uptake was underestimated during each IFC. The only difference in the simulated southern and northern jack pine sites was in their atmospheric forcings; vegetation structure and soil types were the same. These results suggest the model is able to reproduce variability between vegetation types but not within vegetation types.

Evaporation from young secondary vegetation in eastern Amazonia

The fallow vegetation of the slash and burn agriculture in eastern Amazonia is dominated by shrubs and trees. This study of evaporation from such secondary vegetation started when the above-ground parts of the vegetation were approximately 2.5 years old. The results are based mainly on a data set containing 231 days of micrometeorological observations in the period from April 1992 to April 1993. Evaporation values obtained with the Penman open water formula ranged from 1.1 to 7.2 mm d−1, with an overall mean of 4.6 mm d−1. Actual evaporation, calculated with the Bowen ratio approach, varied from 1.2 to 5.9 mm d−1, with an overall mean of 3.9 mm d−1. Due to the high net radiation and vapour pressure deficit, and the evenly distributed moderate rainfall, the actual evaporation was constantly high during the transition between the rainy and dry seasons. In a relatively dry period, water limitations were indicated by a decrease in the actual evaporation compared with the Penman open water evaporation. Day-to-day variability was pronounced in the rainy season. An overall average of 79% of the net radiation was converted to latent heat flux.The annual evaporation was calculated by an interpolation of missing data with the continuously observed net radiation. The total actual evaporation was estimated to be 1364 mm a−1, against rainfall of 1819 mm a−1; the remaining 455 mm were allocated to drainage. When actual evaporation exceeded rainfall during the dry season, there had to be access to water storage down to depths of more than 3 m. We conclude that the young secondary vegetation can re-evaporate an important part of the rainfall input in spite of the marked seasonal distribution of rainfall. Possible regional climatic changes due to deforestation may be less severe in areas where woody secondary vegetation plays an important role in land cover. © 1997 Elsevier Science B.V.

The role of individual terrain units in the water balance of wetland tundra

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 05:31-47 (1995) - DOI: https://doi.org/10.3354/cr005031 The role of individual terrain units in the water balance of wetland tundra Boudreau LD, Rouse WR The water balance of a High Subarctic wetland was measured in a newly established research basin near Churchill, Manitoba, Canada. Measurements spanned the growing season from early June through to the end of August 1991. The watershed was instrumented such that the water budget could be monitored over each of the dominant terrain units. The study basin has 5 major terrain types consisting of sedge-dominated wetland, upland lichen-heath, tundra lakes and ponds, willow-birch wetland, and open spruce forest, in decreasing order of coverage. These terrain units, and the ecosystem as a whole, are representative of coastal wetlands underlain by permafrost in the Hudson Bay Lowland. Runoff and thus streamflow were closely tied to the moisture status of the peatlands and to the depth of the active layer. During 2 unusually dry periods, the peatlands remained wet, which indicates a lack of water mobility when the water table drops below the surface of the wetland. Streamflow response to rainfall during these periods was small in comparison to early summer when the frost table was near the surface, or to wet periods when the water table rose above the surface. Energy balance measurements showed the lakes and ponds to have about 15% higher net radiation than wetlands and 29% greater than upland lichen-heath. From 9 to 18% of net radiation was used in thawing and heating the ground whereas the latent heat flux for the various terrain types utilized from 49 to 83% of net radiation. Even with unusually large rainfalls that occurred in July, evaporation exceeded precipitation over the course of the summer. Despite this, runoff was high and required a large negative change in groundwater storage to account for it. The lichen-heath and ponds exhibited the greatest change in water storage. The drainage of water from the uplands to the lowlands maintained the soil moisture of the peatlands and contributed to streamflow. Each terrain type had a characteristic water balance due to differences in one or more of the hydrologic variables (evapotranspiration, runoff and storage). This has important implications concerning the impact on the water balance of a change in surface cover brought about by a change in climate. Water balance · Energy balance · Wetlands · Evaporation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 05, No. 1. Publication date: February 23, 1995 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 1995 Inter-Research.

Cloud Types and the Tropical Earth Radiation Budget

Nimbus-7 cloud and earth radiation budget data are compared in a study of the effects of clouds on the tropical radiation budget. The data consist of daily averages over fixed 500 sq km target areas, and the months of July 1979 and January 1980 were chosen to show the effect of seasonal changes. Six climate regions, consisting of 14 to 24 target areas each, were picked for intensive analysis because they exemplified the range in the tropical cloud/net radiation interactions. It is found that the net radiation is strongly influenced by the average cloud type and amount present, but most net radiation values could be produced by several combinations of cloud types and amount. The regions of highest net radiation (greater than 125 W/sq m) tend to have medium to heavy cloud cover. In these cases, thin medium-altitude clouds predominate. Their cloud tops are normally too warm to be classified as cirrus by the Nimbus cloud algorithm. In the tropical oceans there are large regions where the total regional cloud cover varies from 20 to 90 percent, but with little regional difference in the net radiation. The monsoon and rain areas are high net radiation regions.

Radiation Balance of Dryland Grain Sorghum as Affected by Planting Geometry1

AbstractThe effects of planting geometry on the radiation balance of dryland grain sorghum (Sorghum bicolor L. cv. DK 46) were studied in a field experiment at the USDA‐ARS Conservation and Production Research Laboratory at Bushland, TX, in 1984 on a Pullman clay loam (a fine, mixed, thermic Torrertic Paleustoll). The objective was to reduce the radiation load on a crop through manipulation of planting geometry and to determine whether that would affect crop productivity. Net radiation was 5% higher over wide compared to narrow rows (0.76 and 0.38 m, respectively) when averaged over three population levels from 33 to 110 days after sowing. East‐west rows had 14% higher net radiation than north‐south rows, averaged over two row spacings. The differences in net radiation were due to daytime responses, presumably shortwave albedo differences. Leaf photosynthesis and transpiration rates and stomatal resistance were measured twice during the grain‐filling period. These measurements, taken 5 days after a period of moderate rains, showed no differences in the plant response due to row spacing or direction treatments. Slightly higher leaf temperatures in the high‐population plots may have been related to greater depletion of plant available water than in medium and low population plots (72, 66, and 67% depletion, respectively). After 2 weeks of drying, narrow‐row and high‐population treatments showed greater stress as evidenced by lower transpiration and photosynthesis rates and higher stomatal resistance and leaf temperature. Soil water depletion was 20% less in narrow than wide rows during a 2‐week period spanning the leaf transpiration measurement dates. Leaf photosynthesis, transpiration, temperature, and stomatal resistance were not affected by differences in net radiation due to row spacing or row direction.

Trickle irrigation timing and its effect on plant and soil water status

Tomato plants on Sinai sand dunes were irrigated daily by drip irrigation. The irrigation was supplied during daytime hours for one field and a short time after sunset for the second. Results showed that daytime irrigation of soil with low water holding capacity increased the yield significantly and improved plant water potential as well as water use efficiency. The dominant component of water balance under these conditions was found to be deep percolation, which accounted for more than 70% of the water budget. Controlling this component rather than soil water status requires measurements of flux as input for managing the quantity of water to be applied. It is concluded that during hours of high net radiation flux, transpiration rate can best compete with deep percolation rate. Based on this conclusion, the use of net radiation flux as input is recommended for the best irrigation timing.

An estimate of the heat balance in an alpine valley in the New Zealand southern Alps

Daily, monthly and annual values of net radiation, soil heat flow, sensible heat flow and evaporative heat loss were measured, or estimated, for the period 15 August, 1969 to 14 August, 1970 at the Chilton valley in the New Zealand southern Alps (altitude 780 m a.s.l.). In the estimation of these values use was made of a regression equation between net radiation and incoming shortwave radiation, drainage lysimeter measurements, and a modified form of the Penman formula for estimating daily values of evapotranspiration. The average values of the energy flows during the study year were: net radiation, 136 ly day−1, soil heat flow, 2 ly day−1, sensible heat flow, −58 ly day−1, and evaporative heat loss, −82 ly day−1. In comparison with the heat balances of other mid-latitude stations, near the west coasts of land masses, the heat balance of the Chilton valley during the study year was noteworthy for (a) a positive mean monthly value of net radiation in winter (b) a net mean monthly flow of sensible heat away from the surface in winter, and (c) the possibility of high monthly and daily mean values of Bowen ratio, owing to soil moisture deficits in months of consistently high net radiation.

Energy balance microclimatic variations on a coastal beach

This report investigates the variation in energy balance microclimate that occurs across a coastal beach on a clear day. Four beach zones differing only in moisture conditions were selected for comparison. The completely dry sand with its high albedo and hot daytime surface temperatures had the lowest daily net radiation total. Over 90 % of this was transferred to the air by sensible heat flux. The saturated sand surface of the swash zone and the water surface of the surf zone had more of a marine climate. The great bulk of the high daily net radiation went into ground storage with most of the rest being used for evaporation. The wet sand zone represented the true transition zone of the beach and displayed a microclimate intermediate between the extremes of dry sand and ocean. Most of the net radiation went for evaporation, whose total was greater than that of the completely moist zones because of higher vapor pressure gradients. A marked difference in microclimate, caused by differing surface moisture-conditions is seen to exist in a very small horizontal distance under conditions of clear skies. Day and night patterns are reversed with differences between zones much more extreme under the influence of the daytime input of solar radiation. DOI: 10.1111/j.2153-3490.1972.tb01552.x

Temperature Regime and Heat Transfer in a Glasshouse at the Daytime

Characteristics of the temperature regime and the heat transfer in ventilated and unventilated glass-houses at the daytime were studied by using numerical technique based on the shooting method described in a previous paper (UCHIJIMA and IWAKIRI, 1970). The results obtained can be summarized as follows:1. Temperature profiles in the unventilated glasshouse under daytime conditions with higher net radiation were characterized byiTs>iTw>oTw>oTa, where iTs, iTw and oTw are temperatures at the floor surface, at the inner and outer surfaces of glasswall, respectively and oTa outside air temperature. Influence of the dryness of air was strongly marked on the temperature at the floor surface (see Fig. 1). Although the difference in wall temperature between dry and wet houses was about 0.5°C at most, the floor temperature in the dry unventilated house was higher by 10 to 20°C than that in the wet house.2. The following relations were obtained from numerical experiments between temperature excess (ΔT=iTa-oTa) of the unventilated glasshouse and net radiation (iS), area ratio (R=As/Aw) and transfer coefficient (ih, oh), ΔT=iS(a+bR), ΔT=αH-β+γ, where As is floor area (cm2), As wall area (cm2), H=oh⋅104 heat transfer coefficient (1y/sec°C) and a, b, α, β and γ are experimental proportionality constants. The temperature excess increased in proportion to the net rediation. A similar net radiation dependence of the temperature excess was also obtained from our experiments made in an unventilated glasshouse (see Fig. 5). Dependence of temperature excess on sensible heat transfer coefficient was approximated by a hyperbolic formula (see Fig. 7). The values of proportionality constants α and β did not vary with dryness, indicating that the shape of hyperbolic curves was independent of dryness. The asymptotic values of each hyperblic curve decreased with increasing heat transfer coefficient.3. By making reasonable assumptions, the heat balance equations of a ventilated glasshouse are expressed by Es=iqs+ihr(iTs-iTw), for floor surface λ/d(iTw-oTw)=ih/2+Rihr(iTs-iTw) for inner surface of glasswall λ/d(iTw-oTw)=fFo+(fohr+oh)(oTw-oTa), for outer surface of glasswall whereEs=(1-ia)τt(Q+q)0-iBs, iqs=ih/1+R[(iTs-iTw)(1-had/2ih)+had/ih(iTs-oTa)], Es and iqs denote respectively the effective heat source and the sensible heat flux at the floor surface (ly/sec). The temperatures (iTs, iTw, oTw) in the above equations are numerically determined by the shooting method on an electronic computer (TOSBAC 3400). Each line in Fig. 9 denotes schematically the temperature profile in the glasshouse with ventilation. The role of heat flux through the glasswall became less dominant with increment of ventilation rate.

The annual march of the topoclimatic spatial patterns of net radiation in southern California

A previously determined model [9], based on the theoretical knowledge of the physical modifications of solar energy by the atmosphere and its transformation at the surface, has been used to determine the monthly distribution of net radiation in southern California at a topoclimatic scale. Parameters utilized in the equations were cloud cover, cloud type, surface albedo, precipitable water vapor, surface temperature, slope angle, slope orientation, elevation, and urban sinog. A remarkable contrast was found between relatively high net radiation values for the littoral and coastal mountains and those of the lower values of the arid eastern parts of southern California.

Thermal Energy Exchange of a Birch Tree and a Spruce Tree at Night

Measurements of thermal radiation from a birch tree (Betula papyrifera) and a spruce tree (Picea glauca) were made on four clear summer nights at five distances from the base of each tree. Slightly higher net radiation values were observed under the spruce crown. A rapid reduction in net radiation was observed on the periphery of the crowns. Ecological relationships dependent on the distribution of infrared radiation are discussed.