Latent Heat Loss Research Articles

Discharging performances of supercooled CH3COONa·3H2O and Na2S2O3·5H2O in the rounded rectangular unit and parametric analysis

Discharging performances of supercooled salt hydrate PCM (phase change material) in the rounded rectangular storage unit are numerically investigated with the developed multiphase model. Comparisons are first made between supercooled Sodium acetate trihydrate (SAT, CH3COONa·3H2O) and Sodium thiosulfate pentahydrate (STP, Na2S2O3·5H2O). Effects of environment temperature for storage (t0), temperature of the working fluid (tf), the area – volume ratio of the unit (A/V) and PCM thermal conductivity are then analyzed. The results showed that STP has 8% less loss of latent heat during the triggering crystallization process whereas lower discharging rate than SAT due to the lower melting point. Decreasing t0 from 14 °C to 6 °C results in 9% more latent heat loss; decreasing tf from 38 °C to 30 °C also shortens the time period for heat release from 4h to 1.8h; higher A/V and k lead to the higher heat transfer rate, for A/V =200 m−1, the discharging time is 4.2h shorter than that for A/V =70 m−1; however, the effect of k is negligible when k is over 1 W m−1 K−1 due to the larger thermal resistance on the side of working fluid. The results provide guidance for design and application of supercooled SAT and STP in rounded rectangular units for energy storage in solar heating systems.

Preparation and properties of novel ceramic composites based on microencapsulated phase change materials (MEPCMs) with high thermal stability

Ceramic composites are widely used in medium/high temperature thermal energy storage (TES) and catalysis. Due to the high latent heat of phase change materials (PCMs), it is an effective method to improve the TES capacity by combining PCMs with ceramic materials. However, PCMs are easy to leak after being heated, so they need to be microencapsulated. Furthermore, for porous ceramic catalytic composites, the leakage of PCMs will block the pores, which seriously hinders their application. In this paper, a novel microencapsulated phase change material (MEPCM) with thermal expansion void was prepared using “double-layer coating, sacrificing inner layer” method. Based on that, two kinds of ceramic composites have been prepared. One is a TES material which composed of alumina, glass frit (GF) and MEPCMs. Thermal analysis results showed that the composite can still maintain stable heat storage performance after 200 melting-solidification cycles with little latent heat loss. Another is a multifunctional porous composite phase change material (CPCM) by loading Ce and Mn as catalyst via solution combustion synthesis (SCS) method, which can be used in low temperature SCR catalysis and other catalytic fields (100–300 °C). Based on MEPCMs with thermal expansion void, the two ceramic composites show great potential in energy storage and catalysis.

Form-stable paraffin/rice straw/polyvinyl alcohol composite phase change material for thermal energy storage

A form-stable phase change material (PCM) based on paraffin was prepared with rice straw as the supporting material. First, a paraffin miniemulsion was prepared by ultrasonication. Then, the paraffin was loaded on rice straw via a vacuum impregnation method. Finally, the paraffin particles loaded on the rice straw were coated by a polyvinyl alcohol (PVA) film. Scanning electron microscopy images confirm the successful loading of paraffin on rice straw and the coating of PVA on the paraffin particles. Differential scanning calorimetry measurements reveal that the prepared material has a high latent heat of 133.4 J/g. The leakage test verifies that the material has a good cycling stability with only 1.6% latent heat loss after 100 consecutive melting-freezing cycles. The prepared form-stable PCM is promising in thermal energy storage.

Influence of ocean salinity stratification on the tropical Atlantic Ocean surface

The tropical Atlantic Ocean receives an important freshwater supply from river runoff and from precipitation in the intertropical convergence zone. It results in a strong salinity stratification that may influence vertical mixing, and thus sea surface temperature (SST) and air–sea fluxes. The aim of this study is to assess the impact of salinity stratification on the tropical Atlantic surface variables. This is achieved through comparison among regional 1/4 $$^{\circ }$$ coupled ocean–atmosphere simulations for which the contribution of salinity stratification in the vertical mixing scheme is included or discarded. The analysis reveals that the strong salinity stratification in the northwestern tropical Atlantic induces a significant increase of SST (0.2 $$^{\circ }$$ C–0.5 $$^{\circ }$$ C) and rainfall (+ 19%) in summer, hereby intensifying the ocean–atmosphere water cycle, despite a negative atmospheric feedback. Indeed, the atmosphere dampens the oceanic response through an increase in latent heat loss and a reduction of shortwave radiation reaching the ocean surface. In winter, the impacts of salinity stratification are much weaker, most probably because of a deeper mixed layer at this time. In the equatorial region, we found that salinity stratification induces a year-round shoaling of the thermocline, reinforcing the cold tongue cool anomaly in summer. The concept of barrier layer has not been identified as relevant to explain the SST response to salinity stratification in our region of interest.

Numerical investigation on the heat flux properties of a thermal manikin in sleeping environments applying task/ambient air conditioning

As an energy-saving equipment, task/ambient air conditioning (TAC) system was widely used in sleeping environment in recent years. The TAC can deliver cooling air directly to the sleeping person, resulting that the micro climate around the human body becomes very critical in the evaluation of human beings’ thermal comfort. Different from sitting and standing, sleeping human body is always at lying posture, and thus at a lower metabolic rate than at waking status. To understand the heat balance between a sleeping body and the surrounding environment, investigation on the heat loss of human body becomes necessary. Hence, a numerical study on the body heat loss characteristics of a thermal manikin at sleeping state in a bedroom utilizing a TAC system was carried out. The convective heat transfer, radiative heat transfer, evaporative heat loss from skin and respiratory heat loss and their ratios were quantitatively analyzed. The results indicate that the convective heat transfer took the first place, accounting for about 80% of the total heat loss, and Latent heat loss accounted for 15.9%–21% of the total heat loss. In addition, the heat loss at different supply conditions was numerically studied. Results showed that the supply air temperature, flowrate and humidity play different effects on body heat loss. Contributions of this study are meaningful for the accurate control of micro climate of human activities.

Long-term variability of Sea Surface Temperature in the Tropical Indian Ocean in relation to climate change and variability

Abstract The long-term change in the sea surface temperature (SST) of the Tropical Indian Ocean (TIO) and the underlying mechanisms are examined in detail by analysing multiple reanalysis datasets and historical simulations of a global climate model. A robust basin-wide warming signal was found in SST, with the highest long-term warming trend (~0.09 ± 0.015 °C decade−1) seen over the north-western and equatorial Indian Ocean regions. The robust warming trend of TIO SST is a dominant warming signal of the global tropical oceans and is largely in phase with similar warming in western Pacific and Atlantic Oceans. The central equatorial Indian Ocean and south TIO regions went through significant warming during recent decades. The weakened cross-equatorial flow and the associated cyclonic winds over the Arabian Sea region have resulted in equatorial westerlies with an enhanced loss of latent heat over the central and eastern equatorial Indian Ocean. The anomalous cyclonic wind stress curl, in turn, caused mixed layer stratifications in the western Indian Ocean. The advective heat transfer from the south-eastern Indian Ocean to the western Indian Ocean and reduced oceanic cooling by vertical processes, overcome the cooling by the net loss of surface heat fluxes, and favor surface warming the TIO.

Thin-film distillation coupled with membrane condenser for brine solutions concentration

A novel concept of film distillation equipped with the membrane condenser (FD-MC) was proposed and implemented for the concentration of brine salt solutions. In this thermo-gradient method, the water was evaporated from the thin liquid film flowing alongside the hot surface, and then directly condensed on the cold surface of the porous membrane placed at the distance of few millimeters from the feed. The change of the membrane positioning from the hot feed solution to the cold water stream (coolant circuit) enables to overcome the common challenges of the membrane distillation process like long-term stability towards pores wetting, membrane scaling, and latent heat loss. Comparing with the air gap membrane distillation with membrane condenser (AGMD-MC), FD-MC demonstrated higher water flux (14.7 kg/m2·h) and stable performance during the concentration of NaCl solution from 50 up to 230 g/kg (microcrystal formation was noticed) even in the presence of organic pollutants (kerosene or surfactants). A mathematical model of heat and mass transfer in FD-MC process was proposed and successfully verified. With the respect to the temperature of hot (40–100 °C) and cold (10–60 °C) circuits, the energy consumption and thermal efficiency of FD-MC process were in the range of 2.7–3.2 MJ/kg and up to 97%, respectively.

Experimental Determination of Pedestrian Thermal Comfort on Water-Retaining Pavement for UHI Adaptation Strategy

Artificial impervious surfaces are one of the most significant factors contributing to urban heat islands (UHIs). Adapting to UHIs is a challenge in achieving thermal comfort. We conducted a quantitative and subjective evaluation of a closely paved novel water-retaining pavement (WR) and a conventional dense-asphalt pavement (AS). We investigated the thermal states of humans based on the human energy balance known as “human thermal load” as an indicator for the assessment, and the original human thermal load method was improved for assessing nonuniform environments such as pavements. We looked for individual thermal perceptions simultaneously. The experiment was conducted in typical summer weather. The surface temperature of the WR was found to be significantly lower, by 9.5 °C, while the air temperature and humidity above both pavements were not significantly different. Thus, air conditions did not directly affect the sensible and latent heat loss. The reflected solar radiation was significantly larger, and the infrared radiation was significantly smaller on the WR than on the AS due to the lower surface temperature from the water evaporation and higher reflectance. Further, the human thermal load at a pedestrian level of 1.5 m was found to be significantly different: 237 W/m2 for AS and 215 W/m2 for WR. In a subjective evaluation, the perceptions of WR tend to be distributed in smaller human thermal load, thereby resulting in a cooler and comfortable sensation. Therefore, we demonstrated that when compared to AS, WR significantly improves thermal comfort.

Estimation of heat exchanges in Boer crossbred goats maintained in a climate chamber.

Exposure of goats to high air temperatures can induce physiological and behavioral adjustments, increasing the dissipation of excess body heat in the latent form, and intensification of the use of these thermoregulatory tools can result in physiological and productive damage to animals. With this, the objective of the research was to quantify the levels of thermal stress and the sensible and latent heat losses of Boer crossbred goats submitted to different air temperatures, in a climatic chamber. Six male crossbred goats of the Boer breed, with an average weight of 25.06±4.43kg and mean age of six months, were grouped using a completely randomized design, with three treatments (air temperatures of the 26, 30 and 34°C, respectively) and six replicates (animals) with 68% relative humidity. The temperature and relative humidity of the air were collected to calculate the temperature and humidity index (THI) and heat exchanges. Were collected the physiological responses rectal temperature (RT) and surface (ST) and respiratory rate (RF), with these data were estimated the heat exchanges by radiation (L), convection (Cr), total sensitive (Gs), latent of the respiratory tract (Er), cutaneous (Ec), total latent (Et) and total heat exchange (Wt). It was found that the THI values were classified as thermal comfort, moderate stress and very stressful, respectively, in the three conditions evaluated. With the increase in AT, the animals significantly increased (P<0.05) the RT, ST and RF, and consequently reduced sensitive heat exchanges, from 38 to 8%, and increased latent heat exchanges, from 62 to 92%, when compared air temperatures of 26 and 34°C, respectively. Physiological responses showed a significant negative (P<0.05) correlation with sensitive heat exchanges and a positive correlation with latent heat exchanges. In very stressful thermal conditions, the animals lost almost all of the excess metabolic heat by latent means (skin and respiratory tract).

Theoretical Minimum Thermal Load in Buildings

Summary Building cooling and heating accounts for a large portion of total global energy use and requires commensurate amounts of resources, which contribute significantly to global warming. Traditionally, addressing this issue has meant improving the efficiency of equipment supplying the thermal energy, reducing envelope heat transfer, and reducing air infiltration. However, this approach is already reaching practical limits. In this perspective, we explore (1) how to reduce thermal load in buildings theoretically and (2) how to achieve that reduction and dramatically lower the energy required to support building loads practically. First, we discuss our framework developed for calculating the theoretical minimum thermal load (TMTL) in buildings. Our analysis shows that current thermal loads in buildings are more than an order of magnitude higher than the TMTL. We also introduce an approximate formula to calculate energy savings from zonal control of thermal load, which shows that the majority of zonal control benefits can be achieved with fewer than 10 zones. Then, we discuss pros and cons of various approaches and strategies to achieve the TMTL. We conclude our perspective with some longer-term R&D ideas, such as thermally adaptive clothing and thermal storage to help approach the TMTL, while providing the additional benefit of interacting with the renewable grid of the future.

Preparation and Performance of Microencapsulated Phase Change Material with Paraffin Core and SiO2 Shell for High Latent Heat and Low Heat Loss by Sol–Gel Method

Microencapsulated phase change materials (MicroPCM) were prepared via sol–gel method using paraffin as heat storage core and silica as inorganic shell. The morphology feature, chemical structure, thermal properties and thermal stability of MicroPCM were characterized by the field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FTIR), the differential scanning calorimeter (DSC), simultaneous thermal analyzer (STA) and the thermal conductivity meter. The results indicated that MicroPCM were spherical in shape with the shell thickness in the range from 236[Formula: see text]nm to 303[Formula: see text]nm. The stirring speed and TEOS dosage were key factor on the latent heat and supercool effect of MicroPCM. The maximum latent heat of MicroPCM was 240.2[Formula: see text][Formula: see text] with the heat loss of only 0.2[Formula: see text][Formula: see text] in phase transformation when it was prepared at the stirring speed of 400[Formula: see text]r/min and TEOS dosage of 20[Formula: see text]ml. MicroPCM was a promising material for thermal energy storage (TES).

Diurnal variability of atmospheric cold pool events and associated air-sea interactions in the Bay of Bengal during the summer monsoon

Atmospheric cold pools generated from convective downdrafts can significantly modulate air-sea interaction processes, though the variability in cold pool events is not yet documented in the Bay of Bengal (BoB). In this study, the seasonal and diurnal variability of cold pool events (defined as a drop in air temperature greater than 1 °C within 30 min) in the BoB is examined using moored buoy measurements with 10-min temporal resolution at 8°N, 12°N, and 15°N along 90°E. The analysis shows that cold pools are plentiful and frequent during summer (May–September) and fall (October–November) compared to winter (December-February) and spring (March–April). Results also indicate a significant diurnal variability at 15°N and 12°N (but not at 8°N) during summer, with more frequent and intense cold pool events in the afternoon. Cold pools lead to an intensification of turbulent heat exchange between the ocean and atmosphere, with increased latent heat loss (~ 80 Wm−2) through both an increase in wind speed and reduction in air specific humidity and increased sensible heat loss (~ 40 Wm−2) due primarily to air temperature drops. There is also a significant diurnal variability in these air-sea exchanges during the summer, with a twofold enhancement in latent and sensible heat fluxes associated with afternoon vs nighttime cold pools events. Finally, we establish the connection between the enhancement of afternoon cold pool events and southeastward propagating synoptic-scale rainfall activity on diurnal time scales from the western BoB.

Impacts of Oceanic Mixed Layer on Hurricanes: A Simulation Experiment With Hurricane Sandy

AbstractInfluences of the ocean mixed layer (OML) dynamics on intensity, pathway, and landfall of October 2012 Hurricane Sandy were examined through an experiment using the Weather Research and Forecasting (WRF) model. The WRF model was run for two cases with or without coupling to the OML. The OML in the WRF was calculated by an oceanic mixed layer submodel. The initial conditions of the depth and mean water temperature of the OML were specified using Global‐FVCOM and Global‐HYCOM fields. The comparison results between these two cases clearly show that including the OML dynamics enhanced the contribution of vertical mixing to the air‐sea heat flux. When the hurricane moved toward the coast, the local OML rapidly deepened with an increase of storm wind. Intense vertical mixing brought cold water in the deep ocean toward the surface to produce a cold wake underneath the storm, with the lowest sea temperature at the maximum wind zone. This process led to a significant latent heat loss from the ocean within the storm and hence rapid drops of the air temperature and vapor mixing ratio above the sea surface. As a result, the storm was intensified as the central sea level pressure dropped. Improving air pressure simulation with OML tended to reduce the storm size and strengthened the storm intensity and hence provided a better simulation of hurricane pathway and landfall.

Far future climate (2060–2100) of the northern Adriatic air–sea heat transfers associated with extreme bora events

The northernmost part of the Mediterranean Sea, the northern Adriatic shelf, is a complex area where the intensity of dense water formation and the consequent Adriatic-Ionian thermohaline circulation are shaped by a combination of extreme wintertime bora winds and substantial freshwater loads. To better understand the impact of global warming on extreme bora dynamics and the associated sea surface cooling, this study applies the Adriatic Sea and Coast (AdriSC) kilometer-scale modelling suite to the far future climate (2060–2100) period. Under both Representative Concentration Pathway (RCP) 4.5 and RCP 8.5 greenhouse emission scenarios, the AdriSC simulations are carried out via the combination of a statistical approach—consisting of an ensemble of 3-day simulations for 22 extreme bora events, and a pseudo-global warning (PGW) methodology—imposing a climatological change to the forcing used to produce the evaluation (present climate) runs. Despite a noteworthy decrease in intensity of the bora winds (by up to 3 m/s), the latent heat losses are simulated to increase (by up to 150 W/m2) due to the reduction in relative humidity in the northern Adriatic (by up to 3%). Consequently, the sea surface cooling associated with severe bora events and preconditioning the dense shelf water formation in the northern Adriatic is projected to not significantly change compared to present climate. Although these results need to be further confirmed, this study thus provides a new view on the future of processes driven by sea surface cooling, such as the dense shelf water formation or the Adriatic-Ionian thermohaline circulation, that were projected to decrease in the future climate by regional climate models an order of magnitude coarser than the AdriSC simulations.

An Economic and Technology Analysis of a New High-Efficiency Biomass Cogeneration System: A Case Study in DC County, China

Biomass is the fourth largest energy source in the world; it is easy to store and can be converted into various kinds of renewable energies. The biomass cogeneration system is an important way to utilize biomass energy, especially in northern China. At present, there are many problems in biomass power plants in China, such as high latent heat loss of chimney and cooling towers, low power generation efficiency, and thermal efficiency. In order to solve this problem, this paper introduces low vacuum circulating water heating technology in the biomass cogeneration system, and expounds the differences between China and Western countries in biomass power plants. Based on this background, the technology is redesigned and reformed to make it more suitable for the biomass fuel varieties in the power plant location, and realize the localization of technology and the expansion of scale. The application of this improved technology in China’s biomass cogeneration project is analyzed. Based on the biomass cogeneration project in the DC County of China, the analysis confirms that the designed low vacuum circulating water heating technology is suitable for biomass power generation projects with agricultural and forestry wastes as raw materials, and its application can greatly improve the heat utilization efficiency of the whole cogeneration system. At the same time, in order to estimate the possibility of profitable investment when the key financial parameters change, the financial risk is analyzed. The results show that the probability of 90% net present value (NPV) in 15 years is between 355.28 million RMB and 623.96 million RMB, and the internal rate of return can reach 17.7%.

Processes Controlling Sea Surface Temperature Variability of Ningaloo Niño

AbstractA high-resolution (3–8 km) regional oceanic general circulation model is utilized to understand the sea surface temperature (SST) variability of Ningaloo Niño in the southeast Indian Ocean (SEIO). The model reproduces eight Ningaloo Niño events with good fidelity and reveals complicated spatial structures. Mesoscale noises are seen in the warming signature and confirmed by satellite microwave SST data. Model experiments are carried out to quantitatively evaluate the effects of key processes. The results reveal that the surface turbulent heat flux (primarily latent heat flux) is the most important process (contribution &gt; 68%) in driving and damping the SST warming for most events, while the roles of the Indonesian Throughflow (~15%) and local wind forcing are secondary. A suitable air temperature warming is essential to reproducing the reduced surface latent heat loss during the growth of SST warming (~66%), whereas the effect of the increased air humidity is negligibly small (1%). The established SST warming in the mature phase causes increased latent heat loss that initiates the decay of warming. A 20-member ensemble simulation is performed for the 2010/11 super Ningaloo Niño, which confirms the strong influence of ocean internal processes in the redistribution of SST warming signatures. Oceanic eddies can dramatically modulate the magnitudes of local SST warming, particularly in offshore areas where the “signal-to-noise” ratio is low, raising a caution for evaluating the predictability of Ningaloo Niño and its environmental consequences.

Investigating the Role of the Tibetan Plateau in the Formation of Atlantic Meridional Overturning Circulation

AbstractThe Tibetan Plateau (TP) over the Eurasian continent has significant effects on both regional and global climate. It can even affect the remote Atlantic meridional overturning circulation (AMOC), as shown in this study. Through coupled modeling experiments, we demonstrate that removing the TP immediately weakens the meridional wind over East Asia, resulting in stronger westerlies in the midlatitudes. The stronger westerlies enhance the southward Ekman flow and surface latent and sensible heat losses in the subpolar North Atlantic, cooling the surface ocean and leading to stronger North Atlantic deep-water formation and stronger AMOC during the first few decades after the TP removal. At the same time, accompanying the weakened trade winds in the tropical Pacific, more moisture is transported from the tropical Pacific to the North Atlantic, freshening the surface ocean and triggering a weakening of the AMOC. The AMOC weakening in turn results in southward expansion and melting of sea ice, providing more freshwater to the North Atlantic, which furthers the weakening of the AMOC. The positive feedback between the AMOC and sea ice eventually leads to AMOC shutdown. We illustrate that there would be no AMOC without the TP. These results call for a revisiting of how ocean circulation and global climate may have responded to the TP uplift and other tectonic changes on the geological time scale.

Inverse Modeling of Global and Regional Energy and Water Cycle Fluxes using Earth Observation Data

AbstractThe NASA Energy and Water Cycle Study (NEWS) climatology is a self-consistent coupled annual and seasonal cycle solution for radiative, turbulent, and water fluxes over Earth’s surface using Earth observation data covering 2000–09. Here we seek to improve the NEWS solution, particularly over the ocean basins, by considering spatial covariances in the observation errors (some evidence for which is found by comparing five turbulent flux products over the oceans) and by introducing additional horizontal transports from ocean reanalyses as weak constraints. By explicitly representing large error covariances between surface heat flux components over the major ocean basins we retain the flux contrasts present in the original data and infer additional heat losses over the North Atlantic Ocean, more consistent with a strong Atlantic overturning. This change does not alter the global flux balance but if only the errors in evaporation and precipitation are correlated then those fluxes experience larger adjustments (e.g., the surface latent heat flux increases to 85 ± 2 W m−2). Replacing SeaFlux v1 with J-OFURO v3 (Japanese Ocean Flux Data Sets with Use of Remote Sensing Observations) ocean fluxes also leads to a considerable increase in the global latent heat loss as well as a larger North Atlantic heat loss. Furthermore, including a weak constraint on the horizontal transports of heat and freshwater from high-resolution ocean reanalyses improves the net fluxes over the North Atlantic, Caribbean Sea, and Arctic Ocean, without any impact on the global flux balances. These results suggest that better characterized flux uncertainties can greatly improve the quality of the optimized flux solution.

The effect of gas to liquid ratio on carbon dioxide removal and heat loss across a forced ventilated trickling filter

The objective of this study was to investigate the effect of the gas: liquid ratio (GLR) on carbon dioxide removal and heat loss across a forced-ventilated trickling filter (TF) used as bioreactor. The effect of 8 different GLRs (1.2–15.7) on carbon dioxide removal and heat loss from water passing a trickling filter were tested in random order. The TF was part of a pilot scale fresh water intensive recirculating aquaculture system and had a media bed height of 1.8 m, a diameter of 0.9 m, a specific surface area of 200 m2/m3 and was operated at a fixed hydraulic surface load of 9.42 m3/m2.h, a mean inlet water temperature of 27.0–27.5 °C, and a mean inlet pH ranging from 7.02–7.12. For each GLR, CO2 removal from water was calculated from CO2 measurements in the inlet and outlet air of the TF using an online infrared probe (developed for agriculture and greenhouses) and from 12 water measurements done once every 3 h during 2 subsequent days. The water inlet CO2 concentrations varied between 4.5–9.0 mg/L (calculated from total inorganic carbon and pH). The results showed that the CO2 removal from water to the air in a trickling filter increased from 3.1 mg/L at a GLR of 1 to 6.1 mg/L for a GLR of 15. The relationship between GLR and CO2 removal could be described as an asymptotic curve with the following equation CO2removal from water(mgL)=6.44-5.82(0.648GLR); (R2 = 0.91). A linear relation between total heat loss across the TF and the applied GLRs showed an average total heat loss of 33.2 kJ per cubic meter of air for all GLRs. Of the total heat loss on average 91 % was latent heat loss and 9 % sensible heat loss. This study showed that: (1) GLRs above 5 will not result in significant additional CO2 removal; (2) energy loss at a GLR of 5 is, under our experimental conditions with a mean inlet air temperature of 22.6 °C and an mean inlet air relative humidity of 66.9 %, 26.0 kJ per g CO2 removed.

Seasonal and spatial variations of air-sea heat exchange in the seas around the Korean Peninsula: Based on the observations and reanalysis products from 2011 to 2016

It is important to better understand air–sea heat exchange for weather and climate systems prediction. In the seas around the Korean Peninsula (KP), the annual cycles of most oceanic and atmospheric variables have long been well recognized, whereas those of the air–sea heat exchange are still not completely clear primarily due to a lack of in-situ observations applied to estimate surface heat flux. This is particularly true over the region affected by the Tsushima Warm Current (TWC), where cold and dry air and a northwesterly wind over the warm sea surface enhance heat exchange during the winter monsoons (when the ocean loses heat), which may often be over or underestimated through atmospheric reanalysis model products. Herein, we present estimates of the mean annual cycles of air–sea heat fluxes from in-situ observations at two locations (I-ORS and ESROB) and from two atmospheric reanalysis products (CFSv2 and MERRA-2) during the period of 2011–2016. The results show that the net heat loss of the ocean (net heat flux (NHF) of −68 Wm-2, positive downward) at ESROB near the east coast of Korea is 146 Wm-2 larger than that (+78 Wm-2, net heat gain) at I-ORS located ~250 km southwest of KP, except in June when the incoming shortwave radiation flux decreases significantly (by 208 Wm-2) only at the I-ORS, a response associated with the meiyu-baiu rain band. Greater sensible and latent heat losses (SHF and LHF) of 32 and 47 Wm-2 during both winter and spring, respectively, and less LHF of 22 Wm-2 during fall, were observed at ESROB than at I-ORS. The CFSv2 yields −24, −84, −41, and −180 Wm-2 (−43, −110, −56, and −120 Wm-2) in terms of the average NHF, winter SHF, and spring and fall LHFs at I-ORS (ESROB), whereas MERRA-2 yields −28, −56, −26, and −161 Wm-2 (−108, −134, −71, and −155 Wm-2), which is indicative of significant biases in the air–sea temperature difference and the wind speed. Spatial distributions of SHF and LHF of both reanalysis products, which are consistent each other and with the observations despite their biases, indicate the significant impact of TWC and the associated currents through the sea surface temperature and saturation-specific humidity on the annual air–sea heat exchange cycles within the region.