differences between IAP and MY are greatest on clear days. The dominance of diffuse radiation on overcast days resulted in slightly higher albedos than on clear and rainy days at both sites, with a more obvious increase at IAP. Under rainy conditions, the surface is wet, hence the decrease in surface albedo (Ao et al., 2016b). The lowest albedo values occurred under rainy conditions, again as expected, at MY. However, at IAP daytime and midday median values of albedo for rainy days were still greater than for clear days. This might be explained by IAP having more and taller buildings, and thus a greater proportion of walls that do not get wet in the rain. Between-site differences in midday median values of albedo were always greater than differences in the daytime median values for any sky conditions, indicating that street canyons play an important role in radiation trapping when solar elevation angles are greater. Based on the summer average, the midday and daytime albedo were 0.10 and 0.11 at IAP, and they were both 0.13 at MY. These values are the same as observed for urban and suburban sites in Basel (Christen and Vogt, 2004), but lower than reported in other city centres [e.g., 0.16, 0.18 - Marseille (Grimmond et al., 2004); 0.14 KSK London (Kotthaus and Grimmond, 2014a, 2014b); 0.14 Shanghai (Ao et al., 2016b)] and suburban sites [e.g., 0.15 Łódź (Offerle et al., 2006b); 0.17 Miami (Newton et al., 2007); 0.24, 0.25- Kansas City (Balogun et al., 2009); 0.18 Oberhausen (Goldbach and Kuttler, 2012)]. Incoming longwave radiation 𝐿 ↓ is primarily influenced by the existence of cloud, boundary layer temperatures, water vapour
The MODIS LST V5 products (MOD11A1 for Terra and MYD11A1 for Aqua satellites) have been validated for a number of mostly homogeneous sites using both temperature-based and radiance-based methods, and in most cases RMSE has been within 1 K (Wan, 2008; Wan and Li, 2008; Coll et al., 2009). Wan (2008) validated MODIS LST over two lake sites and found that MODIS generally underes- timated the temperature during both day and night observa- tions and had a RMSE of 0.7 K. Wan and Li (2008) compared MODIS LST against radiance-based LST in playa, grass- land, lake and bare soil sites and found again that in most cases MODIS LST underestimates ground-based measure- ments, both during the day and night, and errors were usu- ally below 1 K, except for cases of bare soil where they were 1–2 K larger. Finally, Coll et al. (2009) looked at a rice field and a coniferous forest and observed an underestimation of MODIS LST of around −0.3 K with a RMSE of around 0.6 K at the rice field and negligible bias and a RMSE of 0.6 K at the forest site. The main identified causes of the underesti- mation bias were neglection of above-average atmospheric aerosol optical depths and difficulty in filtering out all cloud- affected observations, especially if the cloud cover was not very significant or consisted of cirrus clouds (Wan and Li, 2008). This problem is compounded at night, when it is more difficult to detect clouds (Neteler, 2010). The other identified sources of error were uncertainty in surface emissivities, es- pecially at the bare soil and heterogeneous sites (Wan and Li, 2008) and during the periods of high soil surface sur- face moisture, for example after rain events (Hulley et al., 2010). No correlation, however, was found between VZA or the satellite (Aqua or Terra) and the RMSE, and in general larger errors occurred during the day than at night (Wan and Li, 2008). The prevalent bias (underestimation) in both day and night LST retrievals present in the MODIS LST product would appear to make it highly suitable for application of the DTD approach.
In the last two decades, surfaceenergybalance methods have demonstrated their utility in modeling water availabil- ity using diagnostic retrievals of energyfluxes from in situ or remote sensing data, especially data acquired in the ther- mal infrared (TIR) region (Kalma et al., 2008). While remote sensing estimates of ET over the Arctic exist from global modeling systems (Mu et al., 2009; Zhang et al., 2010), these modeling systems typically do not compute the full energybalance. To estimate energyfluxes at local scales, on the order of hundreds of meters, initiatives such as FLUXNET (http://fluxnet.ornl.gov/) provide eddy covariance flux mea- surements at discrete sites situated in different ecosystems across the US and globally. Unfortunately, there are few mea- surements sites in the Arctic (Mu et al., 2009), making the existing instrument network insufficient to capture pertinent details of the changing Arctic climate and landscape (ACIA, 2004; AMAP, 2012; Serreze and Barry, 2011; Vörösmarty et al., 2001). Detailed process-based (prognostic) land surface models can be also used to estimate coupled water and en- ergy fluxes over landscapes (Duursma and Medlyn, 2012; Ek et al., 2003; Falge et al., 2005; Haverd et al., 2013; Smith et al., 2001; Vinukollu et al., 2012, among others); however, they may neglect important processes that are not known a priori. For example, Hain et al. (2015) demonstrated the value of comparing prognostic and TIR-based diagnostic la- tent heat flux estimates over the continental US to diagnose moisture sources and sinks that were not well-represented in the prognostic modeling system.
The turbulent fluxes are computed with the bulk method, based on differences in temperature, humidity and wind speed between the measurement level and the surface. We use measurements from the upper level, the records from the lower level sensors contain several data gaps. Following Van den Broeke et al. (2005), stability correction functions by Holtslag and De Bruin (1988) and Dyer (1974) are applied for stable and unstable conditions, respectively. A compar- ison of turbulent fluxes calculated with data from either the upper or the lower measurement level revealed that when us- ing wind speed measurements from the upper level, turbulent fluxes are underestimated, mainly on days with low wind speeds. At both AWS sites, the ratio of wind speeds mea- sured at the upper and lower level is always larger than unity for wind speeds above 6 m s −1 ; for lower wind speeds this ra- tio is smaller than unity about 20% of the time. On days with a wind speed maximum below the upper level, the wind is always directed down-slope. Moreover, the temperature dif- ference between the air and the surface is mostly larger than 5 K, suggesting the presence of katabatically driven flow. Al- though wind speeds are relatively low in these circumstances, turbulent fluxes are underestimated considerably by using the upper level measurements, because the temperature differ- ence between the air and the surface is large. To obtain good agreement between turbulent fluxes calculated with the up- per or lower level measurements, we limited the turbulent flux reduction by the stability correction to one third when using the upper level data. For the surface roughness length for momentum (z 0v ) we use constant values of 0.13 mm for
The site Yingke (YK) is located in the artificial oasis to the south of Zhangye city (100 ◦ 24 0 E, 38 ◦ 51 0 N), where the main crop is maize with row structure and regular irrigation. The turbulent heat fluxes and meteorological data were measured with Eddy-Covariance system (EC) and Automatic Weather Station (AWS). Half-hourly averaged turbulent fluxes (H and LE) were computed, while 10-min averages of net radiation and soil heat flux were stored. The measured soil heat flux is the value at the 5cm under the surface for the all sites in this study, and was corrected to the surface by the method of integration using the gradient of soil temperature and the soil heat flux (Liebethal et al., 2005). In addition, 10-min av- erage ancillary meteorological data, such as air temperature, relative humidity, and wind speed were also recorded. About 80% energy closure ratio was found in the EC data. Since the two-layer model requires energy conservation, closure in the flux measurements was enforced through a Bowen-ratio method; that is, Bowen-ratio was calculated using H and LE of the EC measurements, and then H BR and LE BR were re-
Average daily sensible heat fluxes tend to be lower over the aspen compared to the sagebrush during the months when the aspen leaves are actively transpiring (Fig. 5); average daily fluxes ranged from 73 to 88% less than that over the sage- brush during the months from June to August. Interestingly, the diurnal trend in sensible heat flux above the aspen and sagebrush sites are quite similar during the non-snow period (April through November, Fig. 6c). This might be expected, given that the twosites are subject to nearly identical me- teorological forces. Average daily fluxes were more nega- tive above the aspen than the sagebrush during May, Septem- ber and October. Absorption of solar radiation during these months was not offset by transpiration of the aspen, result- ing in a higher proportion of the energy being dissipated by sensible heat flux. However the Bowen ratio, defined as the ratio of sensible to latent heat fluxes, are identical for the twosites during May (1.1) and September (2.2). Although the aspen had higher net radiation, the twosites partitioned the available energy between the turbulent fluxes similarly. In October, the Bowen ratio of the aspen rose further to 3.8 while that for the sagebrush dropped to 1.7; the decrease in October for the sagebrush was likely due to the sagebrush utilizing the precipitation that fell in September and October. Bowen ratios suggest increased water stress as the grow- ing season progressed. A typical value for well-watered veg- etation is 0.2 (Campbell, 1977). Average daily Bowen ra- tios reached a minimum in June with values of 0.63, 0.26, and 0.55 for the sagebrush, aspen, and aspen understory, re- spectively. By August, soil moisture storage within the top 1 m had dropped to nearly its minimum; Bowen ratios rose to 1.71, 0.93, and 2.26, respectively, for August. The high Bowen ratio for the understory in August is in response to the soil profile drying down to at least 1 m, causing the un- derstory to senesce. The relatively low Bowen ratio above the aspen suggests that the aspen trees were able to access deeper water sources.
Abstract. The possibility of observing shallow groundwater depth and areal extent using satellite measurements can sup- port groundwater models and vast irrigation systems man- agement. Moreover, these measurements can help to include the effect of shallow groundwater on surfaceenergy bal- ance within land surface models and climate studies, which broadens the methods that yield more reliable and informa- tive results. To examine the capacity of MODIS in detect- ing the effect of shallow groundwater on land surface tem- perature and the surfaceenergybalance in an area within Al-Balikh River basin in northern Syria, we studied the in- terrelationship between in-situ measured water table depths and land surface temperatures measured by MODIS. We, also, used the SurfaceEnergyBalance System (SEBS) to cal- culate surfaceenergyfluxes, evaporative fraction and daily evaporation, and inspected their relationships with water ta- ble depths. We found out that the daytime temperature in- creased while the nighttime temperature decreased when the depth of the water table increased. And, when the water table depth increased, net radiation, latent and ground heat fluxes, evaporative fraction and daily evaporation decreased, while sensible heat flux increased. This concords with the findings of a companion paper (Alkhaier et al., 2012). The observed clear relationships were the result of meeting both condi- tions that were concluded in the companion paper, i.e. high potential evaporation and big contrast in day-night tempera- ture. Moreover, the prevailing conditions in this study area helped SEBS to yield accurate estimates. Under bare soil conditions and under the prevailing weather conditions, we conclude that MODIS is suitable for detecting the effect of shallow groundwater because it has proper imaging times
2.4. Footprint Analysis
[ 23 ] The measurement footprint represents the spatial
context of the measurement [Schmid, 2002]. The extent of the footprint of EC and scintillometry measurements depends on the measurement height, atmospheric stability, and surface roughness length. When footprint models have been applied to open water in previous studies analytical models have generally been used [i.e., Blanken et al., 2000 ; Tanny et al., 2008], where only the roughness length of the water was considered (a valid assumption at a large water body). Several more complex numerical methods have been adopted in order to try and estimate footprints in complex terrain. The SCADIS (scalar distribution) one- and-a-half-order turbulence closure footprint model [Soga- chev et al., 2002 ; Sogachev and Lloyd, 2004] is an example of a complex footprint model that can evaluate measure- ment footprints over terrain that incorporates a variety of surface types. The full description of the model, equations, and numerical details can be found in Sogachev et al. [2002, 2005]. Sogachev and Sedletski  presented a program based on a simpliﬁed version of SCADIS. The program enables estimation of cross-wind integrated ﬂux footprints in neutrally stratiﬁed ﬂow according to the meth- odology given in Sogachev and Lloyd . The program is called the SCADIS ‘‘footprint calculator.’’
According to García-Cueto et al. (2004) and García-Cueto (2007), the proliferation of manufac- turing and public service activities in Mexicali has implied substantial transformations in land use from agricultural to urban areas in a relatively short time period, with a consequent change in environmental variables. Additionally to the pollution caused by particles, there is now the problem of gases and one of the highest levels of energy consumption (approx- imately 1000 kWh/user monthly) in Mexico. Un- doubtedly, this pattern of consumption is a result of the use of air-conditioning to obtain thermal comfort because of the high temperatures prevailing from the middle of spring until the middle of autumn.
downwelling LW, the mean model biases from December to April are − 16, − 22 and − 40 Wm −2 for ERAI, CERES and ISCCP-FD respectively. There is no indication from in situ studies as to where the true model bias may lie, as in situ studies of downwelling LW measurements have shown un- derestimation by CERES and overestimation by ERAI and ISCCP-FD. For upwelling LW, the biases are 11, 16 and 18 Wm −2 for CERES, ERAI and ISCCP respectively. There is uncertainty in inferring a model bias in net downwelling LW, with negative biases suggested by the satellite datasets but a neutral bias by ERAI. The bias in downwelling and net down LW is somewhat higher towards the North American side of the Arctic and lower on the Siberian side (Fig. 5d, f). The surface radiation evaluation provides clues as to the causes of the HadGEM2-ES ice volume balance bias but also underlines why a more detailed analysis is required to prop- erly quantify these causes. For example, in winter the low downwelling LW bias provides a clear mechanism for the bias in ice freezing. However, the reference datasets also sug- gest a low bias in upwelling LW that at first sight would tend to counteract this. In fact, these biases are fully consistent: a low bias in downwelling LW would be expected to cause a low surface temperature bias, causing both a high bias in ice growth and a low bias in upwelling LW. The qualitative eval- uation fails to capture the full causal relationship; for this, an analysis of exactly how the downwelling LW bias affects sur- face flux, including the upwelling LW response, is necessary. In the summer, meanwhile, the surface radiation evalua- tion suggests that a bias in net SW radiation is responsible for the ice volume balance bias, and that this in turn is re- lated to a surface albedo bias. However, at least two possible drivers of this have been identified: the surface melt onset bias and the underlying ice area bias that is itself likely to be caused by the ice volume balance bias. Quantifying the ex-
two heights (adjusted routinely so as to be 0.2 and 1.7 m above the top of the growing maize canopy). Air tem- peratures were measured using thermistors (designed and supplied by TJ Sauer). Water vapor pressure was cal- culated from hygroclip humidity and temperature probe data (model HC2-S3-L; Rotronic, Switzerland supplied by Campbell Scientific, Inc, Logan, UT). Fans drew air into the intakes, providing a constant flow of ambient air over the sensors at 0.34 m 3 /min. Carbon dioxide concentrations were measured with an absolute, non-dispersive infrared (NDIR) gas analyzer (model LI-820, LI-COR Inc., Lincoln, Nebraska, USA). Air intake openings faced in the direction of the most prevalent winds (near North).
designed to estimate energy partitioning by using satellite and meteorological data. While most of the studies using SEBS derive surfaceenergybalance items located at flat ar- eas (Su et al., 2005; Yang et al., 2010), none of them con- sider the influence of topographical influence. With the de- velopment of satellite sensor grid resolution, when applying SEBS to the high resolution satellite dataset, the topographic influences become increasingly important. Terrain controls how much sky is visible and therefore influences incident diffuse and reflected sky radiation. Since surface solar ra- diation measurement is very sparse in the mountainous re- gion, the knowledge of the terrain is thus important for the radiation balance and further for the surfaceenergybalance in complex terrain (Tovar-Pescador et al., 2006; Aguilar et al., 2010; Long et al., 2010). The aim of this research was to combine a topographically corrected solar radiation (the amount of shortwave radiation received under clear-sky con- ditions) with SEBS over the Tibetan Plateau mountain area. A topographically enhanced surfaceenergybalance system (TESEBS) was developed to generate a series of distribu- tions of surfaceenergybalance in a meso-scale area on the north area of Mt. Qomolangma over the Plateau. Small lakes, rivers, glacier, and surfaces with short canopies are all in- cluded in the study area (Fig. 1).
It is unknown from the current data exactly why the ath- lete was unable to complete the record attempt. An energy deficit situation, and therefore loss of body mass, is com- mon in ultraendurance events [6,16,20,27,31] and there- fore cannot directly account for the failed attempt. The insufficient CHO intake may have contributed, as it has previously been correlated with poor performance  and associated with the onset of fatigue  in ultraen- durance triathlon. Aside from the insufficient CHO intake, the lack of sleep and a compromised immune sys- tem due to an undisclosed viral complaint, could have potentially contributed to the failed attempt. It should be noted however that the athlete had had previous experi- ence at ultraendurance races that involved sleep depriva- tion and his preparation for this event was similar. Conclusion
obtained by simply subtracting riverine OC export from NEP, drainage basin NEP is reduced by between 10% and 23%. This is lower than the DOC flux correction of NEP in peatlands (Yu 2012), similar to Lake Torneträsk in northern Sweden) (Christensen et al. 2007), and much higher than the NHL District in northern US (Buffam et al. 2011) and Öreälven catchment (Jonsson et al. 2007). NEP would be reduced even more if we had used headwater OC export, instead of coastal OC inputs. As river OC originates from soils, we might correct the soil carbon sink by subtracting riverine OC fluxes. This results in a circa 50% reduction of the soil sink in southeast and subarctic Norway, and a switch of the soil in western Norway from sink to source of carbon. The latter appears to be an unreasonable result, from which it may be concluded that either 1) NEP should not be corrected by subtracting riverine OC fluxes, 2) the estimate for the soil sink is too low, or 3) the soil sink should be at least equal to the riverine OC flux to compensate for lateral losses of OC. The latter point might be considered as a way to contribute to validation of regional scale soil carbon sink estimates. For this, better estimates of headwater OC export would be extremely useful. For better quantification and understanding of the role of northern landscapes in the carbon cycle, there is a clear need for
Within the framework of a research project coupling meteorological and hydrological models in mountainous areas a distributed Snow/Soil- Vegetation-Atmosphere Transfer model was developed and applied to simulate the energyfluxes at the land surface atmosphere interface in an Alpine valley (Toce Valley - North Italy) during selected flood events in the last decade. Energyfluxes simulated by the distributed energy transfer model were compared with those simulated by a limited area meteorological model for the event of June 1997. The differences in the spatial and temporal distribution of the energyfluxes simulated by the two models are outlined. The Snow/Soil-Vegetation-Atmosphere Transfer model was also applied to simulate the energyfluxes at the land surface-atmosphere interface for a single cell, assumed to be representative of the Siberia site (Toce Valley), where a micro-meteorological station was installed and operated for 2.5 months in autumn 1999. The Siberia site is very close to the Nosere site, where a standard meteorological station was measuring precipitation, air temperature and humidity, global and net radiation and wind speed during the same special observing period. Data recorded by the standard meteorological station were used to force the energy transfer model and simulate the point energyfluxes at the Siberia site, while turbulent fluxes observed at the Siberia site were used to derive the latent heat flux from the energybalance equation. Finally, the hourly evapotranspiration flux computed by this procedure was compared to the evapotranspiration flux simulated by the energy transfer model.
3.9 ENEGRY BALANCE 3.9.1 Power Balance
Due to the availability of oil palm biomass, palm oil mill itself is able to generate electricity for domestic usage and manufacturing purpose. In the designed mill, mesocarp fiber and palm shell are used as boiler fuel to generate steam. These two solid fuels alone are able to generate more than enough energy to meet the energy demands of a palm oil mill. The steam generated from boiler is sends to turbine for generating electricity. The exhaust steam is then sends to back pressure vessel for production usage. The details power consumption of each station with the total power generated from turbine in the designed palm oil mill is shown in next section.
Figure 3. Instantaneous vorticity surfaces at constant magnitude.
Figure 4. Contour plot of the streamwise mean velocity. Only a small portion of the flow domain near the bump is shown.
Energyfluxes, production and dissipation are now discussed following the background provided in section 3. We recall that the proper phase space involves five dimensions, namely three separations and two center point positions. The results discussed in the following concern the two-dimensional sub-spaces (Y c , r z ) at fixed streamwise stations X c with r x = r y = 0, see figure 5. Figure 6 reports the energyfluxes, Φ r and Φ c , as vectors and the right-hand side of equation (4) as background contour plots. All the terms in equation (2) are normalised with the dissipation −4ε ∗ and, for better visualisation, the vectors are shown in arbitrary units. Proceeding downstream from panel (a) to panel (f) in figure 6, the energy dynamics shows a substantial dependence on the streamwise position X c . Three main regions can be distinguished: the zone before the bump in panel (a), the zone after the bump where the flow is separated in panels (b)-(d) and the well reattached flow region downstream in panel (f).
Limited temperature records are available for the eastern side of the Antarctic Peninsula. Analysis of these records shows that summer warming trends on the east coast of the Peninsula are around 3 times as large as those on the west coast. Furthermore, summer temperatures on the east coast correlate strongly with the strength of the circumpolar westerly winds. Marshall et al.  hypothesized that this pattern of regional climate variability was caused by the interaction of the circumpolar westerly winds with the steep mountain barrier of the Antarctic Peninsula. They suggested that strengthening westerly winds would lead to an increase in the occurrence and/or intensity of warm, downslope Föhn winds to the east of the mountains, which would increase surface melt rates over ice shelves in this region. This hypothesis was supported by studies using the Regional Atmospheric Climate Model (RACMO) at 14 km resolution [van Lipzig et al., 2008] and by observations of a downslope wind event made using an instrumented aircraft [King et al., 2008].
percentage is not higher is mainly due to the requirement of a near-noon overpass for the fitting of the diurnal temperature curve (See Section 2.3.2), in combination with the 1 in 3 days without such overpass for a given location as determined by the orbit and coverage 20
of Aqua and GCOM-W. The multi-year and global record of simultaneous MW-LST and MODIS LST during clear skies will support further calibration of MW-LST to MODIS LST in future investigations. This MW to MODIS calibration was not done in this study but is likely needed to maximize consistency between ALEXI implementations over the globe. In terms of potential for additional sampling through the use of MW-based LST, Fig 2c shows that MW-based estimates for the two ALEXI times are available for 54 % of the days where no MODIS-based estimate is available. Fig 2d depicts the fraction of days where either MODIS or MW-LST can 25
Abstract. A newly developed microwave (MW) land sur- face temperature (LST) product is used to substitute ther- mal infrared (TIR)-based LST in the Atmosphere–Land Ex- change Inverse (ALEXI) modeling framework for estimating evapotranspiration (ET) from space. ALEXI implements a two-source energybalance (TSEB) land surface scheme in a time-differential approach, designed to minimize sensitiv- ity to absolute biases in input records of LST through the analysis of the rate of temperature change in the morning. Thermal infrared retrievals of the diurnal LST curve, tradi- tionally from geostationary platforms, are hindered by cloud cover, reducing model coverage on any given day. This study tests the utility of diurnal temperature information retrieved from a constellation of satellites with microwave radiometers that together provide six to eight observations of Ka-band brightness temperature per location per day. This represents the first ever attempt at a global implementation of ALEXI with MW-based LST and is intended as the first step towards providing all-weather capability to the ALEXI framework.