scholarly journals Impact of Soil Moisture Data Resolution on Soil Moisture and Surface Heat Flux Estimates through Data Assimilation: A Case Study in the Southern Great Plains

2019 ◽  
Vol 20 (4) ◽  
pp. 715-730 ◽  
Author(s):  
Yang Lu ◽  
Jianzhi Dong ◽  
Susan C. Steele-Dunne
Keyword(s):  
Heat Flux ◽  
Soil Moisture ◽  
Spatial Resolution ◽  
Surface Heat Flux ◽  
Root Zone ◽  
Sampling Frequency ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Soil Moisture Data ◽  
Temporal Sampling

Abstract The spatial heterogeneity and temporal variation of soil moisture and surface heat fluxes are key to many geophysical and environmental studies. It has been demonstrated that they can be mapped by assimilating soil thermal and wetness information into surface energy balance models. The aim of this work is to determine whether enhancing the spatial resolution or temporal sampling frequency of soil moisture data could improve soil moisture or surface heat flux estimates. Two experiments are conducted in an area mainly covered by grassland, and land surface temperature (LST) observations from the Geostationary Operational Environmental Satellite (GOES) mission are assimilated together with either an enhanced L-band passive soil moisture product (9 km, 2–3 days) from the Soil Moisture Active Passive (SMAP) mission or a merged product (36 km, quasi-daily) from the SMAP and the Soil Moisture Ocean Salinity (SMOS) mission. The results suggest that the availability of soil moisture observations is increased by 41% after merging data from the SMAP and the SMOS missions. A comparison with results from a previous study that assimilated a coarser SMAP soil moisture product (36 km, 2–3 days) suggests that enhancing the temporal sampling frequency of soil moisture observations leads to improved soil moisture estimates at both the surface and root zone, and the largest improvement is seen in the bias metric (0.008 and 0.007 m3 m−3 on average at the surface and root zone, respectively). Enhancing the spatial resolution, however, does not significantly improve soil moisture estimates, particularly at the surface. Surface heat flux estimates from assimilating soil moisture data of different spatial or temporal resolutions are very similar.

scholarly journals Improving Soil Moisture and Surface Turbulent Heat Flux Estimates by Assimilation of SMAP Brightness Temperatures or Soil Moisture Retrievals and GOES Land Surface Temperature Retrievals

2020 ◽  
Vol 21 (2) ◽  
pp. 183-203 ◽  
Author(s):  
Yang Lu ◽  
Susan C. Steele-Dunne ◽  
Gabriëlle J. M. De Lannoy
Keyword(s):  
Heat Flux ◽  
Soil Moisture ◽  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Turbulent Heat

AbstractSurface heat fluxes are vital to hydrological and environmental studies, but mapping them accurately over a large area remains a problem. In this study, brightness temperature (TB) observations or soil moisture retrievals from the NASA Soil Moisture Active Passive (SMAP) mission and land surface temperature (LST) product from the Geostationary Operational Environmental Satellite (GOES) are assimilated together into a coupled water and heat transfer model to improve surface heat flux estimates. A particle filter is used to assimilate SMAP data, while a particle smoothing method is adopted to assimilate GOES LST time series, correcting for both systematic biases via parameter updating and for short-term error via state updating. One experiment assimilates SMAP TB at horizontal polarization and GOES LST, a second experiment assimilates SMAP TB at vertical polarization and GOES LST, and a third experiment assimilates SMAP soil moisture retrievals along with GOES LST. The aim is to examine if the assimilation of physically consistent TB and LST observations could yield improved surface heat flux estimates. It is demonstrated that all three assimilation experiments improved flux estimates compared to a no-assimilation case. Assimilating TB data tends to produce smaller bias in soil moisture estimates compared to assimilating soil moisture retrievals, but the estimates are influenced by the respective bias correction approaches. Despite the differences in soil moisture estimates, the flux estimates from different assimilation experiments are in general very similar.

scholarly journals Simulations of Processes Associated with the Fast Warming Rate of the Southern Midlatitude Ocean

2010 ◽  
Vol 23 (1) ◽  
pp. 197-206 ◽  
Author(s):  
Wenju Cai ◽  
Tim Cowan ◽  
Stuart Godfrey ◽  
Susan Wijffels
Keyword(s):  
Twentieth Century ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Heat Content ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Ekman Transport ◽  
Content Increase ◽  
Intergovernmental Panel ◽  
Zonal Distribution

Abstract Significant warming has occurred across many of the world’s oceans throughout the latter part of the twentieth-century. The increase in the oceanic heat content displays a considerable spatial difference, with a maximum in the 35°–50°S midlatitude band. The relative importance of wind and surface heat flux changes in driving the warming pattern is the subject of much debate. Using wind, oceanic temperature, and heat flux outputs from twentieth-century multimodel experiments, conducted for the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), the authors were able to reproduce the fast, deep warming in the midlatitude band; however, this warming is unable to be accounted for by local heat flux changes. The associated vertical structure and zonal distribution are consistent with a Sverdrup-type response to poleward-strengthening winds, with a poleward shift of the Southern Hemisphere (SH) supergyre and the Antarctic Circumpolar Current. However, the shift is not adiabatic and involves a net oceanic heat content increase over the SH, which can only be forced by changes in the net surface heat flux. Counterintuitively, the heat required for the fast, deep warming is largely derived from the surface heat fluxes south of 50°S, where the surface flux into the ocean is far larger than that of the midlatitude band. The heat south of 50°S is advected northward by an enhanced northward Ekman transport induced by the poleward-strengthening winds and penetrates northward and downward along the outcropping isopycnals to a depth of over 1000 m. However, because none of the models resolve eddies and given that eddy fluxes could offset the increase in the northward Ekman transport, the heat source for the fast, deep warming in the midlatitude band could be rather different in the real world.

scholarly journals Extratropical cyclone induced sea surface temperature anomalies in the 2013/14 winter

2019 ◽  
Author(s):  
Helen F. Dacre ◽  
Simon A. Josey ◽  
Alan L. M. Grant
Keyword(s):  
Heat Flux ◽  
North Atlantic ◽  
Surface Heat Flux ◽  
Cold Front ◽  
Winter Season ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Extratropical Cyclones ◽  
Sst Cooling

Abstract. The 2013/14 winter averaged sea surface temperature (SST) was anomalously cool in the mid-North Atlantic region. This season was also unusually stormy with extratropical cyclones passing over the mid-North Atlantic every 3 days. However, the processes by which cyclones contribute towards seasonal SST anomalies are not fully understood. In this paper a cyclone identification and tracking method is combined with ECMWF atmosphere and ocean reanalysis fields to calculate cyclone-relative net surface heat flux anomalies and resulting SST changes. Anomalously large negative heat fluxes are located behind the cyclones cold front resulting in anomalous cooling up to 0.2 K/day when the cyclones are at maximum intensity. This extratropical cyclone induced cold wake extends along the cyclones cold front but is small compared to climatological variability. To investigate the potential cumulative effect of the passage of multiple cyclone induced SST cooling in the same location we calculate Earth-relative net surface heat flux anomalies and resulting SST changes for the 2013/2014 winter period. Anomalously large winter averaged negative heat fluxes occur in a zonally orientated band extending across the North Atlantic between 40–60° N. The anomaly associated with cyclones is estimated using a cyclone masking technique which encompasses each cyclone centre and its trailing cold front. North Atlantic extratropical cyclones in the 2013/14 winter season account for 78 % of the observed net surface heat flux in the mid- North Atlantic and net surface heat fluxes in the 2013/14 winter season account for 70 % of the observed cooling in the mid-North Atlantic. Thus extratropical cyclones play a major role in determining the extreme 2013/2014 winter season SST cooling.

The Measurement of Surface Heat Flux Using the Peltier Effect

1989 ◽  
Vol 111 (3) ◽  
pp. 798-803 ◽  
Author(s):  
E. C. Shewen ◽  
K. G. T. Hollands ◽  
G. D. Raithby
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Physical Models ◽  
Peltier Effect ◽  
Absolute Accuracy ◽  
Measuring Surface ◽  
Wide Range

Calorimetric methods for measuring surface heat flux use Joulean heating to keep the surface isothermal. This limits them to measuring the heat flux of surfaces that are hotter than their surroundings. Presented in this paper is a method whereby reversible Peltier effect heat transfer is used to maintain this isothermality, making it suitable for surfaces that are either hotter or colder than the surroundings. The paper outlines the theory for the method and describes physical models that have been constructed, calibrated, and tested. The tested physical models were found capable of measuring heat fluxes with an absolute accuracy of 1 percent over a wide range of temperature (5–50°C) and heat flux (15–500 W/m2), while maintaining isothermality to within 0.03 K. A drawback of the method is that it appears to be suited only for measuring the heat flux from thick metallic plates.

Dynamic Calibration of a Coaxial Thermocouples for Short Duration Transient Measurements

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Rakesh Kumar ◽  
Niranjan Sahoo
Keyword(s):  
Heat Flux ◽  
Finite Element ◽  
Heat Conduction ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Dynamic Calibration ◽  
One Dimensional ◽  
Surface Heat Fluxes ◽  
Heat Loads

Coaxial thermocouple sensors are suitable for measuring highly transient surface heat fluxes because the response times of these sensors are very small (∼0.1 ms). These robust sensors have the flexibility of mounting them directly on the surface of any geometry. So, they have been routinely used in ground-based impulse facilities as temperature sensors where rapid changes in heat loads are expected on aerodynamic models. Subsequently, the surface heat fluxes are predicted from the transient temperatures by appropriate one-dimensional heat conduction modeling for semi-infinite body. In this backdrop, the purpose of this work is to design and fabricate K-type coaxial thermocouples in-house and calibrate them under similar nature of heat loads by using simple laboratory instruments. Here, two methods of dynamic calibration of coaxial thermocouples have been discussed, where the known step loads are applied through radiation and conduction modes of heat transfer. Using appropriate one dimensional heat conduction modeling, the surface heat fluxes are predicted from the measured temperature histories and subsequently compared with the input heat loads. The recovery of surface heat flux from laser based calibration experiment under-predicts by 4% from its true input heat load. Similarly, recovery of surface heat flux from the conduction mode calibration experiments under-predicts 6% from its true input value. Further, finite-element based numerical study is performed on the coaxial thermocouple model to obtain surface temperatures with same heat loads as used in the experiments. The recovery of surface temperatures from finite element simulation is achieved within an accuracy of ±0.3% from the experiment.

Measurements of Burnout Conditions for Flow of Boiling Water in a Vertical Annulus

1964 ◽  
Vol 86 (3) ◽  
pp. 393-404 ◽  
Author(s):  
K. M. Becker ◽  
G. Hernborg
Keyword(s):  
Heat Flux ◽  
Surface Heat Flux ◽  
Flow Model ◽  
Film Flow ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Nonuniform Heating ◽  
Steam Quality ◽  
Internal Heating ◽  
Inner Surface

The present paper deals with measurements of burnout conditions for flow of boiling water in an annulus with an inner diameter of 9.92 mm, an outer diameter of 17.42 mm, and a heated length of 608 mm. Data were obtained in respect of external heating only, internal heating only, and dual uniform and nonuniform heating. The following ranges of variables were studied and 978 burnout measurements were obtained. Pressure: 8.5 < p < 37.5 kg/cm2; Inlet subcooling: 60 < Δtsub < 205 deg C; Steam quality: 0.10 < x < 0.91; Inner surface heat flux: 0 < (q/A)i < 303 W/cm2; Outer surface heat flux: 0 < (q/A)0 < 374 W/cm2; Mass velocity: 71 < m˙/F < 961 kg/m2sec. The results are presented in diagrams where the burnout steam qualities, xBO, were plotted against the pressure with the surface heat fluxes as parameters. The data have been correlated by curves. The scatter of the data around the curves is less than ±5 percent. In the case of equal heat fluxes on both walls of the annulus, burnout always occurred on the inner wall, and the data compared rather well with round duct data. When the annulus was heated internally only, the data showed very low burnout values in comparison with the results for dual heating and round ducts. This disagreement was explained by considering the climbing film flow model and by the fact that only a fraction of the channel perimeter was heated. For external heating the data are somewhat lower than corresponding round duct data, but rather high in comparison with internal heating. The climbing film flow model was also used to interpret this observation. For dual nonuniform heating it was found that the outer surface may be overloaded from 30 to 70 percent compared with the inner surface without reducing the margin of safety in respect to burnout for the annulus. It was further observed that when the heat flux for the wall on which burnout occurs is increased, the burnout steam quality for the channel decreases. If, however, the heat flux for the opposite wall is increased, the burnout steam quality also increases. It was also observed that the highest burnout values are obtained when burnout occurs simultaneously on both cylinders. Finally, the results have been compared with annuli and rod cluster data in published works, and a method for predicting burnout conditions in rod clusters has been proposed.

What balloon soundings can tell about surface heat flux partitioning

2020 ◽  
Author(s):  
Jasper Denissen ◽  
Hendrik Wouters ◽  
René Orth ◽  
Diego Miralles ◽  
Ryan Teuling
Keyword(s):  
Heat Flux ◽  
Soil Moisture ◽  
Land Surface ◽  
Surface Heat Flux ◽  
Sensible Heat Flux ◽  
Surface Heat ◽  
Atmospheric Measurements ◽  
Flux Partitioning ◽  
Temperature And Humidity ◽  
Soil Moisture Availability

&lt;p&gt;The land surface can influence near-surface weather. This happens, amongst others, through the impact of soil moisture availability on surface heat fluxes: when soil moisture is unavailable in soil moisture-limited conditions, most of the available energy will be used for heating the air above the land surface (sensible heat flux). But as soil moisture increases, evapotranspiration (latent heat flux) increases, affecting the surface heat flux partitioning. At the point that ample soil moisture is available in energy-limited conditions, the surface heat flux partitioning remains unaffected by soil moisture. The atmospheric boundary layer (ABL) responds to changes in surface heat flux partitioning in particular in terms of its temperature and humidity. Based on these mechanisms, observations of boundary layer dynamics should allow to infer the large-scale land surface state.&lt;/p&gt;&lt;p&gt;The goal of this study is to use atmospheric measurements of temperature and humidity to estimate the surface heat flux partitioning. This is achieved by constraining an ABL model (CLASS4GL) with the vertical temperature and humidity profiles as observed by thousands of soundings of hot air balloons across the globe. In CLASS4GL, the initial soil moisture is adjusted to yield matching modelled versus observed vertical temperature and humidity profiles. By doing so, the resulting surface fluxes are inferred exclusively from atmospheric measurements.&lt;/p&gt;&lt;p&gt;We find that ABL&amp;#8217;s tend to higher, warmer and drier in water-limited conditions. This largely results from changes in soil moisture availability, which mainly affects the sensible heat flux and consequently, the surface heat flux partitioning. We determine the critical soil moisture, which distinguishes between soil moisture- and energy- limited conditions, using the ratio between the sensible- and latent heat flux and independent satellite surface soil moisture.&lt;/p&gt;&lt;p&gt;This is the first time that balloon soundings are used globally to assess the critical soil moisture. This research will help to further improve our understanding of land-atmosphere feedbacks and foster a correct representation of land surface characteristics in Land Models and subsequently, Climate Models.&lt;/p&gt;

Surface Heat Flux Variations across the Kuroshio Extension as Observed by Surface Flux Buoys

2010 ◽  
Vol 23 (19) ◽  
pp. 5206-5221 ◽  
Author(s):  
Masanori Konda ◽  
Hiroshi Ichikawa ◽  
Hiroyuki Tomita ◽  
Meghan F. Cronin
Keyword(s):  
Heat Flux ◽  
Spatial Patterns ◽  
Surface Heat Flux ◽  
Kuroshio Extension ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Wind Condition ◽  
Northerly Wind ◽  
Monsoon Wind ◽  
The Kuroshio

Abstract Wintertime sea surface heat flux variability across the Kuroshio Extension (KE) front is analyzed using data from the Kuroshio Extension Observatory (KEO) buoy in the Kuroshio recirculation gyre south of the KE front and from the Japan Agency for Marine–Earth Science and Technology KEO (JKEO) buoy in the north of the front. The coincident data used are from periods during two winters (2007 and 2008), when both buoys had a complete suite of meteorological data. In these two winter periods, the focus of this research is on three types of typical weather patterns referred to here as the northerly wind condition, the monsoon wind condition, and the normal condition. During the northerly wind condition, latent and sensible heat fluxes were large and often varied simultaneously at both sites, whereas during the monsoon wind condition the latent heat flux at the KEO site was significantly larger than that at the JKEO site. The difference between these heat flux patterns is attributed to the different airmass transformations that occur when prevailing winds blow across the KE front versus along the front. Reanalysis products appear to reproduce these heat flux spatial patterns at synoptic scales. It is suggested that the relative frequencies of these different types of weather conditions result in anomalous spatial patterns in the heat fluxes on monthly time scales.

The Role of Surface Heat Fluxes on the Size of Typhoon Megi (2016)

2021 ◽  
Author(s):  
Li-Zhi Shen ◽  
Chun-Chieh Wu ◽  
Falko Judt
Keyword(s):  
Heat Flux ◽  
Surface Heat Flux ◽  
Inner Core ◽  
Outer Region ◽  
Outer Core ◽  
Surface Heat ◽  
Core Region ◽  
Heat Fluxes ◽  
Secondary Circulation ◽  
Surface Heat Fluxes

AbstractThis study attempts to understand how surface heat fluxes in different storm regions affect tropical cyclone (TC) size. The Advanced Research Weather Research and Forecasting (ARW-WRF) model (version 3.5.1) is used to simulate Typhoon Megi (2016). A series of numerical experiments are carried out, including a control simulation and several sensitivity experiments with surface heat fluxes suppressed in different TC regions [to mimic the reduction of the Wind-Induced Surface Heat Exchange (WISHE) feedback in the inner and/or outer core]. The results show that with surface heat fluxes suppressed in the entire domain, the TC tends to be smaller. Meanwhile, the TC size is more sensitive to the surface heat flux change in the outer core than to that in the inner core. Suppressing surface heat fluxes can weaken the rainbands around the suppressed area, which in turn slows down the secondary circulation. When the surface heat flux is suppressed in the inner-core region, the weakening of the secondary circulation associated with the diminished inner rainbands is limited to the inner core region, and only slightly affects the absolute angular momentum import from the outer region, thus having negligible impact on TC size. However, suppression of surface heat fluxes in the outer-core region leads to less active outer rainbands and a more substantial weakening of secondary circulation. This results in less absolute momentum import from the outer region, and in turn, a smaller TC.

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