Changes In Heat Flux Research Articles

The Role of Internal Variability in Twenty‐First‐Century Projections of the Seasonal Cycle of Northern Hemisphere Surface Temperature

AbstractThe seasonal cycle is fundamental to the Earth's climate system, accounting for the vast majority of temperature variance. Understanding how the seasonal cycle will change in the future, and by when, is a key question with important implications. Here a 40‐member initial condition climate model ensemble is used to investigate the influence of internal variability on the detection of changes in the amplitude and timing of the seasonal cycle of surface temperature over Northern Hemisphere land in response to increasing greenhouse gases. Internal variability renders the detection of these changes challenging; even by the mid‐twenty‐first century, small ensembles will be insufficient to separate the forced signals from internal variability over many continental regions in the Northern Hemisphere. Despite this, projected changes over Europe, North Africa, and Siberia are large and easily detectable, even in a single member. Specifically, amplitude increases over Europe and North Africa while it decreases over Siberia. On the other hand, the timing of the seasonal cycle is delayed over all three regions. It is found that these changes are remarkably robust across model ensembles from the Coupled Model Intercomparison Project phase 5 archive. To understand the mechanisms underlying these robust changes, a simple energy balance model is used to partition changes into contributions arising from changes in the physical parameters that control the seasonal cycle. It is found that future changes in the seasonal cycle over the three regions are most strongly controlled by changes in surface longwave and turbulent heat fluxes.

Impacts of Land-Use Data on the Simulation of Surface Air Temperature in Northwest China

This study examines the impacts of land-use data on the simulation of surface air temperature in Northwest China by the Weather Research and Forecasting (WRF) model. International Geosphere–Biosphere Program (IGBP) landuse data with 500-m spatial resolution are generated from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite products. These data are used to replace the default U.S. Geological Survey (USGS) land-use data in the WRF model. Based on the data recorded by national basic meteorological observing stations in Northwest China, results are compared and evaluated. It is found that replacing the default USGS land-use data in the WRF model with the IGBP data improves the ability of the model to simulate surface air temperature in Northwest China in July and December 2015. Errors in the simulated daytime surface air temperature are reduced, while the results vary between seasons. There is some variation in the degree and range of impacts of land-use data on surface air temperature among seasons. Using the IGBP data, the simulated daytime surface air temperature in July 2015 improves at a relatively small number of stations, but to a relatively large degree; whereas the simulation of daytime surface air temperature in December 2015 improves at almost all stations, but only to a relatively small degree (within 1°C). Mitigation of daytime surface air temperature overestimation in July 2015 is influenced mainly by the change in ground heat flux. The modification of underestimated temperature comes mainly from the improvement of simulated net radiation in December 2015.

Impacts of Changes in Sea Ice and Heat Flux on Arctic Warming

The reduction of Arctic sea ice has enhanced the sea-ice-air interaction in the Arctic atmospheric boundary layer, especially the increase in sea-air heat flux in autumn. Changes in radiation and heat flux and the role of sea-ice-air interactions in climate change in the central Arctic were analyzed and evaluated on the basis of the observation data of ice stations during the six Chinese Arctic Research Expeditions. The albedo is high in the Arctic sea-ice surface except the melting process. Overall, the Arctic sea-ice surface can absorb radiation energy, which is much lower than that absorbed by mid-latitude surfaces. Consequently, a relatively weak turbulence exchange occurred between the sea-ice surface and the atmosphere. Further estimates of the surface heat budget in the Arctic are obtained using eddy correlation and flux-profile method. The results are representative of the heat balance and ice-air interactions in the central Arctic Ocean. In the Arctic, changes in heat flux displayed notable interdecadal characteristics, similar to the change of sea-ice extent. The heat flux in September of each year in 2001-2014 was considerably higher compared with that in 1979-2000, particularly at the edges of the central Arctic Ocean. In September of each year in 1979-2014, the sea-ice extent was remarkably negatively correlated to the heat flux (sensible heat flux + latent heat flux), and the heat flux was considerably positively correlated to the atmospheric temperature at 2 m above sea level. This result demonstrates that a reduction of Arctic sea ice will lead to changes in heat flux, thereby warming the atmosphere and increasing the temperature of the atmospheric boundary layer over the Arctic. In addition, this impact is long-lasting.

Impacts of the Sahel-Sahara Interface Reforestation on West African Climate: Intra-Annual Variability and Extreme Temperature Events

The impacts of the reforestation of the Sahel-Sahara interface on the seasonal distribution of the surface temperature and thermal extremes are studied in the Sahel (West African region lying between 11&#176N and 18&#176N). We performed a simulation with the standard version of the RegCM4 model followed by another one using the altered version of the same model taking into account an incorporated forest. The impacts of the vegetation change are assessed by analyzing the difference between the two runs. The reforestation may influence strongly the frequency of warm days (TG90P) and very warm days (TX90P) by decreasing it over the reforested zone from March to May (MAM) and the entire Sahel during the June-August (JJA) period. These TG90P and TX90P indices decrease may be due to the strengthening of the atmospheric moisture content over the whole Sahel region and the weakening of the sensible heat flux over the reforested zone. The analysis also shows a decrease of the TN90P indice (warm nights) over the Sahel during the wet season (JJA) which could be partly associated with the strengthening of the evapotranspiration over the whole Sahel domain. The analysis of additional thermal indices shows an increase of the tropical nights over the entire Sahel from December to February (DJF) and during the warm season (MAM). The strengthening of the tropical night is partly associated with an increase of the surface net downward shortwave flux over the reforested zone. When considering the heat waves, an increase (a decrease) of these events is recorded over the southern Sahel during JJA and SON periods (over the whole Sahelian region during DJF), respectively. Changes in latent heat flux appear to be largely responsible for these extreme temperatures change. This work shows that the vegetation change may impact positively some regions like the reforested area by reducing the occurrence of thermal extremes; while other Sahel regions (eastern part of the central Sahel) could suffer from it because of the strengthening of thermal extremes.

Thermal Analysis of a Zirconium Dioxide Coated Aluminum Alloy Piston

Performance and operating costs are the most important factors in internal combustion engines. It is one of the most commonly used methods to coat pistons with advanced technological ceramic materials in order to improve performance and fatigue life in internal combustion engines. In this study, changes in temperature and heat flux were investigated in various thickness coatings made on a 2500 cc turbo diesel engine piston. As bonding coat, NiCrAl was used in a thickness of 0.2 mm, while ZrO2 (zirconium dioxide) was used in thicknesses of 0.2-0.4-0.6 and 0.8 mm as thermal barrier coating material. The piston was modeled in PTC Creo parametric software and then transferred to ANSYS Workbench environment to create a mathematical model. Engineering calculations were also done using the finite element method. After the calculation, the temperatures at the depth of 5 mm from the combustion chamber upper surface, the binder layer upper surface, the thermal coating upper surface and the combustion chamber upper surface were compared. As a result, it was observed that the combustion chamber and the section at the depth of 5 mm from the combustion chamber had a temperature decrease of 13%.

Decadal variability in summer precipitation over eastern China and its response to sensible heat over the Tibetan Plateau since the early 2000s

This study investigates the decadal variations in summer precipitation over eastern China (SPEC) and its response to the decadal change of sensible heat (SH) flux over the Tibetan Plateau (TP). The results show that SPEC experiences a significant decadal change in approximate 2003, demonstrating positive rainfall anomalies over central China and negative anomalies over northeast, north, and south China. Meanwhile, a noticeable increase in SH over the TP occurs in the early 2000s at the decadal time scale. Further analysis reveals that when spring SH over the TP is abnormally strong, there will be a stronger atmospheric heat source and development of deep convection over the TP in the forthcoming summer. The positive thermal forcing induces an abnormal anticyclonic circulation and airflow divergence in the upper layer and cyclonic circulation and airflow convergence in the mid‐layer over the TP. And the negative vorticity and positive geopotential height anomalies in the upper layer over the TP and south China leads to the strengthening of the South Asian High (SAH) and the northwestern Pacific subtropical high (NWPSH). As a result, cold and dry air from higher latitudes and warm and humid air from the tropics converge over central China and diverge over north and south China. In addition, there exist a strong ascending motion over central China and an anomalous descending motion over south China due to the positive diabatic heating and horizontal temperature advection anomalies over central China and negative anomalies over south China. On the other hand, the circulation conditions strengthen the East Asian summer monsoon and weaken the South China Sea summer monsoon. Ultimately, more moisture is transported into central China, but less into south China, which give rise to positive and negative rainfall amounts in the corresponding areas, respectively.

Seasonal variation of precipitation over the Indochina Peninsula and its impact on the South China Sea spring warming

This study documents the seasonal variation of precipitation over the whole Indochina Peninsula (ICP) and associated changes in atmospheric winds and surface heat fluxes and investigates the impact of the ICP precipitation‐related heating and circulation on spring sea surface warming in the South China Sea (SCS). Climatologically, most of the ICP experiences the rainy season from May to October and the period from November to April is the dry season. The summer wet‐winter dry pattern dominates the seasonal rainfall variation in most regions and the maximum rainfall along the west coast occurs during June through August in association with monsoon westerly winds. A pronounced semi‐annual rainfall variation is observed along central Vietnam with a primary peak in October and a secondary peak in May, which is related to northeasterly and southwesterly winds, respectively. Surface heat fluxes change drastically over the ICP in March–April and play an important role in increasing the thermal contrast with the neighbouring waters and heating the atmospheric column, which causes upward motion and precipitation over the ICP. The induced compensatory downward motion over the northern SCS leads to an increase in downward shortwave radiation and a decrease in surface wind speed and turbulent heat fluxes, which contributes to the SCS warming before the summer monsoon onset.

Increasing Atlantic Ocean Heat Transport in the Latest Generation Coupled Ocean‐Atmosphere Models: The Role of Air‐Sea Interaction

AbstractRecent increases in resolution of coupled ocean‐atmosphere models have the potential to improve the representation of poleward heat transport within the climate system. Here we examine the interplay between model resolution‐dependent changes in Atlantic Ocean heat transport (AOHT) and surface heat fluxes. The different roles of changes in atmospheric and ocean resolution are isolated using three different climate models (The Centro Euro‐Mediterraneo sui Cambiamenti Climatici Climate Model 2, Hadley Centre Global Environmental Model 3 – Global Coupled configuration 2, and European Community Earth‐System Model 3.1) and comparing runs in which (a) only the ocean resolution changes, (b) only the atmosphere resolution changes, and (c) both change. Enhancing ocean resolution from eddy parameterized to eddy permitting increases the AOHT throughout the basin, values changing from 1.0 to 1.2 PW at 26°N, bringing the AOHT into the range of estimates from the RAPID observing array. This increase in AOHT is associated with higher North Atlantic sea surface temperatures and increased ocean heat loss to the atmosphere. Increasing the atmospheric resolution alone has little impact on the AOHT due to regionally compensating changes in the components of the net heat flux. Finally, in a fourth experiment the impact of resolution changes in both components and the transition to an eddy‐resolving ocean is assessed. This additional resolution increase is accompanied by a further change in the AOHT and improves agreement with observations in the tropics but not the subpolar regions. However, unlike with the increase to the eddy‐permitting ocean, when the greatest AOHT change occurs in the subtropics and subpolar region, the most significant increase now occurs in the tropics.

Effect of initial stress and Hall current on a magneto-thermoelastic porous medium with microtemperatures

In this paper, the effect of initial stress on a thermoelastic porous medium with microtemperatures in the presence of magnetic field taking Hall current into account is investigated. The medium is permeated by a strong transverse magnetic field imposed perpendicularly on the displacement plane so the induced electric field is neglected. The normal mode analysis is used to obtain the exact expressions for displacement components, normal conduction current density field, transverse conduction current density field, microtemperature components, heat flux moments, stress components, temperature distribution and change in the volume fraction field. The variations of the considered variables with the horizontal distance are illustrated graphically. The results of comparisons we obtained were with and without initial stress and Hall current effect. Some particular cases of special interest have been deduced from the present investigation.

Role of North Indian Ocean Air–Sea Interaction in Summer Monsoon Intraseasonal Oscillation

Air–sea coupling processes over the north Indian Ocean associated with the Indian summer monsoon intraseasonal oscillation (MISO) are investigated. Observations show that MISO convection anomalies affect underlying sea surface temperature (SST) through changes in surface shortwave radiation and surface latent heat flux. In turn, SST anomalies may also affect the MISO precipitation tendency ( dP/ dt). In particular, warm (cold) SST anomalies can contribute to increasing (decreasing) precipitation rate through enhanced (suppressed) surface convergence associated with boundary layer pressure gradients. These air–sea interaction processes are manifest in a quadrature relation between MISO precipitation and SST anomalies. A local air–sea coupling model (LACM) is formulated based on these observed physical processes. The period of the LACM is proportional to the square root of seasonal mixed layer depth H, assuming other physical parameters remain unchanged. Hence, LACM predicts a relatively short (long) MISO period over the north Indian Ocean during the May–June monsoon developing (July–August monsoon mature) phase when H is shallow (deep). This result is consistent with observed MISO characteristics. A 30-day-period oscillating external forcing is also added to the LACM, representing intraseasonal oscillations propagating from the equatorial Indian Ocean to the north Indian Ocean. It is found that resonance will occur when H is close to 25 m, which significantly enhances the MISO amplitude. This process may contribute to the higher MISO amplitude during the monsoon developing phase compared to the mature phase, which is associated with the seasonal cycle of H.

Effect of Air‐Sea Environmental Conditions and Interfacial Processes on Extremely Intense Typhoon Haiyan (2013)

AbstractTyphoon Haiyan (2013) intensified rapidly and reached a central pressure of 895 hPa over the warm northwestern Pacific. To clarify why Haiyan became such an extraordinarily intense tropical cyclone (TC), we investigated the impacts of atmospheric and oceanic conditions and air‐sea interfacial processes on Haiyan's intensity. We performed ensemble experiments with many different initial oceanic conditions and a 7‐km‐mesh atmosphere‐wave‐ocean coupled model. We also performed sensitivity experiments to examine the impacts of sea spray and use of a 2‐km‐mesh horizontal resolution. Also, analogous experiments were performed with Typhoon Mike (1990), which followed a similar track but was less intense than Haiyan. For both TCs, ocean coupling helped alleviate uncertainty in the simulated intensities caused by different preexisting oceanic conditions. Increases in air‐sea latent heat fluxes helped increase the intensity of both TCs although the effect of sea spray depended on whitecap coverage. Preexisting oceanic conditions and air‐sea interfacial processes directly affected the secondary circulation via changes in latent heat fluxes and near‐surface moisture influxes. However, the 2‐km‐mesh resolution improved only Haiyan's simulation; the mean latent heat flux over the strength area was insufficient to simulate the intensity. It was easterly winds and specific humidity at 850 hPa that determined the small size, rapid translation, less sea surface cooling, and small decreases in latent heat fluxes beneath the frictional convergence area of simulated Haiyan. Understanding of the effect of preexisting oceanic conditions and air‐sea interfacial processes on simulated TCs will serve as a guideline for improvement of the atmosphere‐wave‐ocean coupled model.

Exact solution of shock wave structure in a non-ideal gas under constant and variable coefficient of viscosity and heat conductivity

This paper investigates the structure of a normal shock wave using the continuum model for steady one-dimensional flow of a viscous non-ideal gas under heat conduction. The coefficients of viscosity and heat conductivity are assumed to be directly proportional to a power of the temperature. The simplified van der Waals equation of state for the non-ideal gas has been assumed in this work. The smooth and rough sphere models of the gas molecules in the kinetic theory of gases are used for the viscosity of a non-ideal gas. Assuming the Prandtl number to be 3 / 4, the complete integral of the energy equation, exact velocity, density, pressure, Mach number, change in entropy, viscous stress, and heat flux across the shock transition zone have been obtained in a perfect and a non-ideal gas under both constant and variable properties of the medium. The validity of the continuum hypothesis with respect to Mach number is examined for the study of shock wave structure in both the smooth and rough sphere models of ideal and non-ideal gas molecules. It has been shown that the continuum theory gives reasonably valid results for flows with higher Mach numbers in the case of a non-ideal gas in comparison with an ideal gas. The inverse thickness of the shock wave is calculated and compared for constant and variable properties of the gases. The shock wave thickness is also discussed as a function of mean free path of the gas molecules computed at different points between the boundary states. It is found that the inverse shock thickness decreases with the increase in non-idealness of the gas. In the rough sphere model of gas molecules, the increase in the non-idealness of the gas and the temperature exponent in the coefficients of viscosity and heat conductivity significantly increases the validity limit of the continuum model.

Atmospheric heat advection in the Kara Sea region under main synoptic processes

Atmospheric studies document both a periodic variability in the winter temperatures in the Kara Sea region related to internal Arctic climate variability and a recent trend of winter warming—one of the strongest warming trends in the whole Arctic. This study aims to analyse side by side with other energy budget terms the contribution of horizontal heat and moisture advection to the observed recent warming. The atmospheric energy budget terms vertically integrated from the surface up to 500 hPa are estimated using the ERA‐Interim reanalysis for the period 1979–2014. The core of this study is to relate variability and changes in heat fluxes in the Kara Sea region to synoptic‐scale processes using the Russian weather‐type classification system. Singular spectrum analysis is applied to the heat flux data which were previously stratified into changes due to changes in frequency and due to changes in amplitude. We have shown that the multi‐decadal variations in the horizontal heat advection (now on a rising phase) are comparable to the positive trend in the turbulent heat fluxes due to sea ice reduction, although relatively weaker. We have also found that the changes in sensible heat flux (a constant increase in the first principal component since 1999) is a general regional feature and not related to any weather pattern, while the changes in horizontal heat advection are clearly related to the changes in frequency of the weather type A (characterized by a low‐pressure system in the central Arctic surrounded by high pressure in the continents, winds of S, S‐W direction and a positive horizontal heat advection and surface temperature anomaly over the Kara Sea) which are periodic in nature with a period of about 22 years. In recent years (at least until 2012) not only is warm air advection, associated with A type, more frequent, but it also brings much more energy from the continent to the Kara Sea compared to the reference period (1980–1990). This is most probably related to the increase in the radiatively forced surface air temperature at the source.

Effect of microgravity on flow boiling heat transfer of liquid hydrogen in transportation pipes

The flow boiling phenomenon of liquid hydrogen (LH2) during transportation in microgravity is very different from that under terrestrial condition. In this study, a saturated flow boiling of LH2 in a horizontal tube has been simulated under microgravity condition using coupled level-set and volume of fluid method. The validation of the developed model shows good agreement with the experimental data from the literature. The changes of heat fluxes and pressure drops under different gravitational accelerations were analyzed. And, the variation of heat fluxes with different wall superheat and contact angle were compared between microgravity (10−4g) and normal gravity (1g) condition. Also, the influence of surface tension were studied under microgravity. The numerical results indicate that the heat flux decrease with the decrement of gravitational acceleration. And the heat transfer ratio decrease with the increment of wall superheat in the nucleate boiling regime. The heat transfer slightly reduce when considering surface tension. In addition, the changes of contact angle have a more significant impact on heat transfer under microgravity condition.

The leading interannual variability modes of winter surface air temperature over Southeast Asia

The present study analyzes the leading interannual variability modes of Southeast Asian surface air temperature (SAT) during boreal winter. The first Empirical Orthogonal Function (EOF1) mode displays same-sign SAT anomalies over Southeast Asia, with a center around the north Indo-China Peninsula and south China. The second EOF (EOF2) shows a dipole SAT anomaly pattern between the Indo-China Peninsula and south China. Surface heat flux change may not be able to explain SAT variation related to the EOF1, but explain partly the SAT change associated with the EOF2. Atmospheric anomalies play a crucial role in the SAT variations via wind-induced temperature advection. Specifically, for the EOF1, marked northerly anomalies appear over the Southeast Asia, which bring colder air from higher latitude and contribute to negative SAT anomalies. Change in the intensity of Arctic Oscillation, Siberian High and La Nina like sea surface temperature (SST) anomalies over the tropical central-eastern Pacific play a key role in forming the northerly anomalies related to the EOF1. For the EOF2, at the lower troposphere, a pair of anomalous cyclones appears over the tropical north and south Indian Ocean, together with southwesterly wind anomalies extending from the Indian Ocean to the Indo-China Peninsula, which favor positive SAT anomalies there. Formation of the twin cyclones is likely to be a Gill type Rossby wave response of the tropical Indian Ocean SST warming. At the upper troposphere, two wave trains, one originated from the Arctic region and another from the Mediterranean Sea, contribute collectively to the atmospheric circulation anomalies over Southeast Asia related to the EOF2.

Global and Arctic climate sensitivity enhanced by changes in North Pacific heat flux

Arctic amplification is a consequence of surface albedo, cloud, and temperature feedbacks, as well as poleward oceanic and atmospheric heat transport. However, the relative impact of changes in sea surface temperature (SST) patterns and ocean heat flux sourced from different regions on Arctic temperatures are not well constrained. We modify ocean-to-atmosphere heat fluxes in the North Pacific and North Atlantic in a climate model to determine the sensitivity of Arctic temperatures to zonal heterogeneities in northern hemisphere SST patterns. Both positive and negative ocean heat flux perturbations from the North Pacific result in greater global and Arctic surface air temperature anomalies than equivalent magnitude perturbations from the North Atlantic; a response we primarily attribute to greater moisture flux from the subpolar extratropics to Arctic. Enhanced poleward latent heat and moisture transport drive sea-ice retreat and low-cloud formation in the Arctic, amplifying Arctic surface warming through the ice-albedo feedback and infrared warming effect of low clouds. Our results imply that global climate sensitivity may be dependent on patterns of ocean heat flux in the northern hemisphere.

Seasonal and Interannual Mixed‐Layer Heat Budget Variability in the Western Tropical Atlantic From Argo Floats (2007–2012)

AbstractOceanic and atmospheric processes were investigated in order to explore the causes of seasonal and interannual variability of sea surface temperatures (SST) in the western tropical Atlantic (WTA; 20°S–20°N, 15°W–60°W). A mixed‐layer (ML) heat budget was performed by using Argo profiles and supplementary data sets based on satellite and atmospheric products during the period 2007–2012. The WTA is divided into four boxes which represent the main temporal and spatial heterogeneities of this region. An analysis of error of each term pointed out that the mean net surface heat fluxes are systematically underestimated by 20 W m−2. A correction of this term provides realistic estimates of the vertical mixing which was obtained as residual term. In agreement with previous studies, the results show that surface flux is the most important process that governs the seasonal cycle of the heat content. Changes in shortwave radiation and latent heat fluxes dictate the oceanic response to the meridional migration of the ITCZ. Along the equator, surface fluxes modulate the annual cycle of ML temperature, but are strongly balanced by horizontal advection. The entrainment term proves a small contribution to the cooling of the ML. On an interannual time scale, the strong positive (negative) SST anomalies observed in 2010 (2012) were generated during the previous winter in both years, mainly north of 10°N, during which the wind anomalies were at the origin of intense heat loss anomalies. Horizontal advection may contributes to the maintaining of these SST anomalies in the equatorial zone and south Atlantic.

A High‐Resolution Land Model With Groundwater Lateral Flow, Water Use, and Soil Freeze‐Thaw Front Dynamics and its Applications in an Endorheic Basin

AbstractHuman water regulation, groundwater lateral flow, and the movement of frost and thaw fronts (FTFs) affect soil water and thermal processes, as well as energy and water exchanges between the land surface and atmosphere. Reasonable representation of these processes in land surface models is very important to improving the understanding of land‐atmosphere interactions. In this study, mathematical descriptions of groundwater lateral flow, human water regulation, and FTFs were synchronously incorporated into a high‐resolution community land model, which is then named the Land Surface Model for Chinese Academy of Sciences (CAS‐LSM). With a series of atmospheric forcings and high‐resolution land surface data from the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) program, numerical simulations of the period 1981–2013 using CAS‐LSM with 1‐km resolution were conducted for an endorheic basin, the Heihe River Basin in China. Compared with observations, CAS‐LSM reproduced the distributions of groundwater, evapotranspiration, and permafrost reasonably and well matched the temporal changes in ground temperature, heat fluxes, and FTFs. Results illuminate the temporal and spatial characteristics of frozen soil and the changes in the land‐atmosphere exchange of carbon, water, and energy. The permafrost and seasonally frozen soil were distinguished. In the seasonally frozen areas, the maximum soil frost depth increased by 0.65 mm/year within natural areas and decreased by 2.12 mm/year in human‐dominated areas. The active layer thickness increased 8.63 mm/year for permafrost. In the permafrost zone evapotranspiration and latent heat flux increased, and the sensible heat flux declined. In the human‐dominated areas water use raised the latent heat flux and reduced the sensible heat flux, net ecosystem exchange, and streamflow recharging to the eco‐fragile region in the lower reaches. Results suggested that the land surface model CAS‐LSM is a potential tool for studying land surface processes, especially in cold and arid regions experiencing human interventions.

Analysis of extended micro-Graetz problem in a microtube

In this numerical study, hydrodynamically developed but thermally developing forced convection in a microtube subjected to a step change in the wall heat flux is analysed using a finite-volume method. The slip velocity and temperature jump conditions at the wall and the axial conduction in the fluid are included in the analysis. The combined effects of the Peclet number and the Knudsen number on the local Nusselt numbers as well as on the wall and bulk temperatures are determined in the continuum and slip flow regimes (0 ≤ Kn ≤ 0.1). In the entrance region, large reductions are observed in the Nusselt number with decreasing Peclet number or increasing Knudsen number. The results also show that the thermal length increases with decreasing Peclet number.

Impact of Land‐Sea Thermal Contrast on the Inland Penetration of Sea Fog Over the Coastal Area Around the Korean Peninsula

AbstractBased on the difference between sea surface temperature (SST) and sea air temperature (SAT), sea fog can be classified as cold sea fog (SST < SAT) or warm sea fog (SST > SAT). First, two sea fog events over the Yellow Sea are selected and simulated using Weather Research and Forecasting model. The two sea fogs are designated as cold and warm types, and cooling and moistening rates of each case are calculated to understand the contributions of major factors to the sea fog formation. Turbulence plays a role in the cooling (warming) of the sea air, while advection is responsible for sea air warming (cooling) during the cold (warm) sea fog event. Thus, these two effects cancel each other out. However, the longwave radiative cooling effect is as stronger as or stronger than the other effects in both cases. We conducted sensitivity tests of SST and land skin temperature, which induced obvious changes in turbulent heat flux and land‐sea thermal contrast, respectively. In the increased (decreased) SST experiments, sea fog evaporates (expands) because of more (less) heat transfer from sea to air. The land skin temperature experiments show that increases (decreases) in land‐sea air temperature differences hinder (favor) sea fog penetration.