Warm Moist Air Research Articles

Comparison of therapeutic effects between a new warm moist air device assisted with eyelid massage and eyedrops with only eyedrops for meibomian gland dysfunction

Background Meibomian gland dysfunction (MGD) is a common eye disease that leads to ocular surface damage.Conventional treating method is hot compress with heating pads or warm towels combined with eyelid massage, but the temprature of heat source is difficult to ensure precisely.A new warm moist air device is used in ophthalmology now, however, its clinical effect for MGD is under evaluation. Objective This study was to evaluate the therapeutic effects of a new warm moist air device assisted with eyelid massage for MGD. Methods A randomized-controlled clinical trail was performed.Sixty MGD patients were recruited in Tonghua Eye Hospital from January to June 2015.The patients were divided into two groups according to random number table with matched age, gender and the findings of ocular surface, and the unilateral eyes of the patients were used to analysis.The eyes in the trail group received topical administration of polyethylene glycol eye drops and new warm moist air device combined with eyelid massage, and the eyes in the control group received only topical administration of polyethylene glycol eye drops.The eye examinations were carried out before treatment and 2, 4 weeks after treatment, including ocular surface disease index questionnaire (OSDI), meibomian gland function under the slit lamp microscope, breakup time of tear film (BUT), corneal fluorescein staining scores and Schirmer Ⅰtest (SⅠt). The treating results over time were intergrouply compared.This study protocol was approved by Ethic Committee of Tonghua Eye Hospital, and written informed consent was obtained from each patient prior to entering the group. Results All the patients finished this therapeutic process.In the trail group, the OSDI scores were 13.29±4.06 and 9.29±3.21 at 2 and 4 weeks after treatment, which were significantly lower than those in the control group (16.82±3.21 and 15.41±4.03) (t=-3.5, -6.12, both at P 0.05). In addition, there were not significant differences in SⅠt and meibomian gland secretory levels over time between two groups (SⅠt: Fgroup=0.10, P>0.05; Ftime=0.72, P>0.05; secretion: Fgroup=1.64, P>0.05; Ftime=0.92, P>0.05). Conclusions This new warm moist air device assisted with eyelid massage and polyethylene glycol eye drops can effectively treat MGD, and this combination therapy appears to have a favorable therapeutic effects in comaprison with only polyethylene glycol eye drops. Key words: Meibomian gland dysfunction/therapy; Ocular surface diseases/therapy; Tear film; Prospective study; Randomized-controlled clinical study; Water vapor heating apparatus, ophthalmology/therapeutic use

Cutaneous water collection by a moisture-harvesting lizard, the thorny devil (Moloch horridus).

Moisture-harvesting lizards, such as the Australian thorny devil, Moloch horridus, have the remarkable ability to inhabit arid regions. Special skin structures, comprising a micro-structured surface with capillary channels in between imbricate overlapping scales, enable the lizard to collect water by capillarity and transport it to the mouth for ingestion. The ecological role of this mechanism is the acquisition of water from various possible sources such as rainfall, puddles, dew, condensation on the skin, or absorption from moist sand, and we evaluate here the potential of these various sources for water uptake by M. horridus The water volume required to fill the skin capillary system is 3.19% of body mass. Thorny devils standing in water can fill their capillary system and then drink from this water, at approximately 0.7 µl per jaw movement. Thorny devils standing on nearly saturated moist sand could only fill the capillary channels to 59% of their capacity, and did not drink. However, placing moist sand on skin replicas showed that the capillary channels could be filled from moist sand when assisted by gravity, suggesting that their field behaviour of shovelling moist sand onto the dorsal skin might fill the capillary channels and enable drinking. Condensation facilitated by thermal disequilibrium between a cool thorny devil and warm moist air provided skin capillary filling to approximately 0.22% of body weight, which was insufficient for drinking. Our results suggest that rain and moist sand seem to be ecologically likely water sources for M. horridus on a regular basis.

In this issue of Weather

A great variety is presented on the pages of Weather this month. We begin with an investigation of a severe thunderstorm in Ankara, Turkey. Many readers will know that Turkey is prone to thunderstorms, in part due to its high ground and the additional lift given to airstreams crossing the country. Severe thunderstorms are a particularly significant aspect of the weather, in particular, to aviation, because of their association with large hail, lightning strikes and turbulence, both within and around cumulonimbus clouds. Tuncay Özdemir and Ali Deniz clearly explain the synoptic situation that led to the case they describe in ‘Severe thunderstorm over Esenboğa International Airport in Turkey on 15 July 2013’ illustrated by a range of observed data and ending with a summary of consequences in and around the Turkish capital.In recent decades, there has been significant evolution of our knowledge of the weather systems that lie along the boundary of warm moist air from the south and cooler drier air to its north and there has been considerable discussion on the pages of this journal. The perception that the current method used to show these weather systems leads to many misconceptions has led Bob Owens to write our next paper ‘Fronts – who needs them?’ A provocative piece, this should lead all readers to think about many aspects of our science, including education and the communication of ideas.Next we move onto a study of ‘The general features of tropical Sumatra squalls’ by Jeff Lo and Thomas Orton. These mesoscale features form in periods of relatively light winds, bringing heavy rain and thunderstorms to Singapore and the trade route through the Malacca Strait, affecting the population and shipping through the area, as well as aircraft using Singapore International Airport. This little‐studied phenomenon will add important detail to our knowledge of local weather in the humid tropics.This month's issue concludes with ‘Long‐term observations of increasing snow cover in the western Cairngorms’ by Christopher Andrews, Stephen Ives and Jan Dick. As the authors state, it might be thought that, in a warming world, snow cover might diminish, in particular in areas where snow is ephemeral. However, the trend in the western Cairngorms (but not reflected everywhere in the Scottish Highlands) in the years since 2002 has been an increase – by a substantial margin – and the time between the first day of snow and the last has increased in this area.

Comparison of the multi-scale features in two persistent heavy rainfall events in the middle and lower reaches of Yangtze River

Two persistent heavy rainfall (PHR) events in the middle and lower reaches of Yangtze River (MLYR) occurring in June 1982 and 1998 are studied in this paper. Though both events happened in the Meiyu season, their large-scale background and developing processes were quite different. During the PHR event in 1982, the Lake Baikal area was occupied by a strong westerly trough and the western Pacific subtropical high (WPSH) was stronger and more westward-extending than the normal years. Under such a condition, the cold–dry air and warm–moist air were continuously transported to the MLYR and favored the PHR there. For the event in 1998, the WPSH was similar to that in 1982, while the westerly trough in the Lake Baikal area was comparatively weak and a shortwave trough situating in East China contributed to advect cold–dry air to the MLYR. It is found that the high-latitude trough was closely related to the 10–30-day low-frequency oscillation while the anomaly of WPSH was linked with the combined effect of both 30–60- and 10–30-day low-frequency oscillations in the PHR event in 1982. By contrast, the 60-day low-pass perturbation demonstrated positive impact on the westward extension of WPSH and development of the Baikal trough while the 30–60-day oscillation played a role in strengthening the shortwave trough in East China and the WPSH in the case of 1998. Though the low-latitude 30–60-day oscillations contributed to the intensification and westward extension of the WPSH in both PHR events, their evolution exhibited evident differences. In the 1982 case, the 30–60-day anomalies originated from the western Indian Ocean were much more like the Madden–Julian Oscillation, while its counterpart in the 1998 case was much more similar to the first mode of the boreal summer intraseasonal oscillation.

Impacts of Gulf of Mexico SST Anomalies on Southern Plains Freezing Precipitation: ARW Sensitivity Study of the 28–30 January 2010 Winter Storm

AbstractIce storms are an infrequent but significant hazard in the U.S southern Great Plains. Common synoptic profiles for freezing precipitation reveal advection of low-level warm moist air from the Gulf of Mexico (GOM), above a shallow Arctic air mass ahead of a midlevel trough. Because the GOM is the proximal basin and major moisture source, this study investigates impacts of varying GOM sea surface temperature (SST) on the thermodynamic evolution of a winter storm that occurred during 28–30 January 2010, with particular emphasis on the modulation of freezing precipitation. A high-resolution, nested ARW sensitivity study with a 3.3-km inner domain is performed, using six representations of GOM SST, including control, climatological mean, uniform ±2°C from control, and physically constrained upper- and lower-bound basin-average anomalies from a 30-yr dataset. The simulations reveal discernable impacts of SST on the warm-layer inversion, precipitation intensity, and low-level dynamics. Whereas total precipitation for the storm increased monotonically with SST, the freezing-precipitation response was more varied and nonlinear, with the greatest accumulation decreases occurring for the coolest SST perturbation, particularly at moderate precipitation rates. Enhanced precipitation and warm-layer intensity promoted by warmer SST were offset for the highest perturbations by deepening of the weak 850-hPa low circulation and faster eastward progression associated with enhanced baroclinicity and diabatic generation of potential vorticity. Air-parcel trajectories terminating within the freezing-precipitation region were examined to identify airmass sources and modification. These results suggest that GOM SST can affect the severity of concurrent ice-storm events in the southern Great Plains, with warmer basin SST potentially exacerbating the risk of damaging ice accumulations.

2014年1月28日伊犁河谷暴雪天气的诊断分析

利用常规观测资料、NCEP资料以及多普勒雷达资料，对2014年1月28日伊犁地区特大暴雪进行分析。结果表明：暴雪过程与高空冷槽、南支暖湿气流以及中低空切变有着密切联系；高空偏西急流，加强了整层的上升运动，为强降雪的发生提供了有利的大尺度环流条件；长时间强的水汽输送为暴雪天气提供了充沛的水汽条件；低空辐合、高空辐散的高低空配置有利于暴雪的出现。 By using conventional meteorological observational data and Necp data and Doppler radar data, a heavy snow process on January 28, 2014 in Yili region was diagnosed. It is concluded that the storm is in a stable atmospheric circulation background. The results indicate that the heavy snow process is related to high altitude cold trough, warm moist air flows south branch and shear in the middle and lower level. High altitude by west rapids strengthened the upward movement of the whole layer and provided the favorable large scale circulation condition for the happening of the heavy snow. Long time strong water vapor transport for blizzard weather provides abundant water vapor conditions. Low-level convergence and upper divergence of empty configuration is advantageous to the blizzard.

The Dynamics of Australian Monsoon Bursts

Abstract The wet season of the Australian monsoon is characterized by subseasonal periods of excessively wet or dry conditions, commonly known as monsoon bursts and breaks. This study is concerned with the synoptic evolution prior to monsoon bursts, which are defined here by abrupt transitions of the area-averaged rainfall over the tropical parts of the Australian continent. There is large variability in the number of monsoon bursts from year to year and in the time interval between consecutive monsoon bursts. Reanalysis data are used to construct a lag composite of the sequence of events prior to a monsoon burst. It is determined that a burst in the Australian monsoon is preceded by the development of a well-defined extratropical wave packet in the Indian Ocean, which propagates toward the Australian continent in the few days leading up to the onset of heavy rainfall in the tropics. As in previous studies on the monsoon onset, the extratropical disturbances propagate equatorward over the Australian continent. These extratropical systems are accompanied by lower-tropospheric airmass boundaries, which also propagate into low latitudes. Ahead of these boundaries, relatively warm moist air is advected from the surrounding oceans, locally increasing the convective available potential energy. Commonly employed climate indices show that monsoon bursts are more likely to occur when the active phase of the Madden–Julian oscillation is in the vicinity of Australia. Neither El Niño–Southern Oscillation nor the southern annular mode has a significant impact on the occurrence of monsoon bursts.

An analysis of an extreme rainstorm caused by the interaction of the Tibetan Plateau vortex and the Southwest China vortex from an intensive observation

A rainstorm caused by the coupling of the Tibetan Plateau vortex (TPV) and the Southwest China vortex (SWCV) in eastern Sichuan during 29 June–2 July 2013 is analyzed by using the conventional observed data and its time intensive observed data, the intensive observed data of SWCV scientific experiment during flood season. The results show that under the control of a large transverse trough in Eurasia region at mid-high latitude, the westerly flow in northern China leads TPV eastward movement. And SWCV moves northeastward. Finally, both of them merge to form a combined vortex (CBV) in Sichuan Basin resulting in heavy rainfall. The water vapor from both the Bay of Bengal and the South China Sea provides the sufficient humidity condition. The intensive observation clearly reveals the nascent states of TPV and SWCV, the movements and interactions, especially, the two vortices' merging process, and the effects of cold and warm advection, as well as the rainstorm. When the two vortices merge into CBV, cold tongue and warm flow meet and produce frontogenesis around the center of CBV. A frontogenetical area exists deeply from lower troposphere to upper troposphere with the south-positive and north-negative vertical structure, which is similar to front. The positive PV evidently developed both in the range and in the intensity with the stronger center at upper level, and the positive PV center located at the front of CBV has indicative significance for the vortex’s activities. And CBV has the same distributions of vorticity and temperature with SWCV and TPV, respectively. SWCV and TPV make different key contributions to the dynamic–thermodynamic property of CBV, but both of them have obvious influences on the divergence distribution of CBV. Furthermore, rainfall mainly distributes in the high areas of averaged temperature deviation gradient, and it is closely related to the joint influences of warm-moist air from the south and dry-cold air from the north. But, only using the conventional observed data, it is difficult to obtain the above useful understanding. So, augmenting intensive observation, improving scientific experiment, and focusing on fine study are much conducive for the meso-scale and small-scale weather systems such as SWCV and TPV, as well as its weather influences.

Causes for different spatial distributions of minimum Arctic sea-ice extent in 2007 and 2012

Satellite records show the minimum Arctic sea ice extents (SIEs) were observed in the Septembers of 2007 and 2012, but the spatial distributions of sea ice concentration reduction in these two years were quite different. Atmospheric circulation pattern and the upper-ocean state in summer were investigated to explain the difference. By employing the ice-temperature and ice-specific humidity (SH) positive feedbacks in the Arctic Ocean, this paper shows that in 2007 and 2012 the higher surface air temperature (SAT) and sea level pressure (SLP) accompanied by more surface SH and higher sea surface temperature (SST), as a consequence, the strengthened poleward wind was favorable for melting summer Arctic sea ice in different regions in these two years. SAT was the dominant factor influencing the distribution of Arctic sea ice melting. The correlation coefficient is–0.84 between SAT anomalies in summer and the Arctic SIE anomalies in autumn. The increase SAT in different regions in the summers of 2007 and 2012 corresponded to a quicker melting of sea ice in the Arctic. The SLP and related wind were promoting factors connected with SAT. Strengthening poleward winds brought warm moist air to the Arctic and accelerated the melting of sea ice in different regions in the summers of 2007 and 2012. Associated with the rising air temperature, the higher surface SH and SST also played a positive role in reducing summer Arctic sea ice in different regions in these two years, which form two positive feedbacks mechanism.

Diagnostic Analysis of a Historical Extreme Snow Process in Shandong

Based on conventional surface data,reanalysis data from NCEP and TBB data,the comprehensive analysis of snowstorm occurred in Shandong province from 19 to 20 April 2013 was done. The results showas following. It is the main synoptic background to generate the snowstorm that 500 h Pa upper trough,700 h Pa southwest lowlevel jet and the shear line and 850 h Pa low-level northeaster made the backflowsnow. During the snowshorm,snowstorm area physical quantity in the space above the vertical section shows: A relative humidity of 90% or more under high humidity area downloaded and warm moist air along the southern low-level cold climbed,and after reach a certain height,the water vapor condenses snow,and snowstorm fell the center of the area was not located in the strong upward movement,but located in the north side of the center value biggest,between 28°N ~ 40°N has a high energy frontal zone,and along with the increase of latitude leaning to high altitude. Near the ground layer is an obvious convergence field,and distribution of TBB reaction during the snow-storm had meso-microscale system coordination,TBB maximum in between- 45 ~- 40 ℃. Terrain in the extreme blizzard events over a rapid decline in the temperature played a very important role.

The Blue LED Nobel Prize: Historical context, current scientific understanding, human benefit

The Blue LED Nobel Prize: Historical context, current scientific understanding, human benefit

In this issue ofWeather

We start with the report by Nick Grahame et al. about a thunderstorm event in 2014. Although summer is the main time of year we can expect large-scale storms in the UK, the event of 13–14 June was unusual, in that it occurred in a polar maritime airstream, rather than in the more usual humid tropical air advected from the south. A combination of warm moist air near the surface with dry air of high PV aloft, as well as an inhibiting cap above the boundary layer made conditions perfect for the generation of these storms, which affected many parts of southern England. This is an interesting case study for all wanting to know more about stormy weather. Next we move on to an account of unusual significant weather conditions noted on duty in southern England by Met Office Observer Nigel Paice. His fascinating 35-year account, through his career, illustrates extreme weather events including dense fog, the inland penetration of a sea breeze, exceptional thunderstorms and even a dust devil! The increasing number of students of weather and the environmental sciences has brought the need for students to have access to high quality modelled weather data and ManUniCast is designed to fulfil that need. David Schultz et al. describe their forecast display system, which can be used on tablets, as well as PCs, and its possible application in the classroom and in the field. This system will undoubtedly be useful to all wishing to know how to interpret weather data, then use it sensibly. Finally, we move on to Richard Worthington's account of the association of convection with mountain-wave activity over Wales and Cross Fell in the North Pennines, illustrated by high-resolution satellite imagery. Although vertical motion must be part of a wave train, there is little acknowledgement of its association with convection.

Why the South Pacific Convergence Zone is diagonal

During austral summer, the majority of precipitation over the Pacific Ocean is concentrated in the South Pacific Convergence Zone (SPCZ). The surface boundary conditions required to support the diagonally (northwest–southeast) oriented SPCZ are determined through a series of experiments with an atmospheric general circulation model. Continental configuration and orography do not have a significant influence on SPCZ orientation and strength. The key necessary boundary condition is the zonally asymmetric component of the sea surface temperature (SST) distribution. This leads to a strong subtropical anticyclone over the southeast Pacific that, on its western flank, transports warm moist air from the equator into the SPCZ region. This moisture then intensifies (diagonal) bands of convection that are initiated by regions of ascent and reduced static stability ahead of the cyclonic vorticity in Rossby waves that are refracted toward the westerly duct over the equatorial Pacific. The climatological SPCZ is comprised of the superposition of these diagonal bands of convection. When the zonally asymmetric SST component is reduced or removed, the subtropical anticyclone and its associated moisture source is weakened. Despite the presence of Rossby waves, significant moist convection is no longer triggered; the SPCZ disappears. The diagonal SPCZ is robust to large changes (up to ±6 °C) in absolute SST (i.e. where the SST asymmetry is preserved). Extreme cooling (change <−6 °C) results in a weaker and more zonal SPCZ, due to decreasing atmospheric temperature, moisture content and convective available potential energy.

Atmospheric Boundary Layer Structure and Turbulence during Sea Fog on the Southern China Coast

Abstract Small-scale turbulence has an essential role in sea-fog formation and evolution, but is not completely understood. This study analyzes measurements of the small-scale turbulence, together with the boundary layer structure and the synoptic and mesoscale conditions over the life cycle of a cold advection fog event and a warm advection fog event, both off the coast of southern China. The measurement data come from two sites: one on the coast and one at sea. These findings include the following: 1) For cold advection fog, the top can extend above the inversion base, but formation of an overlaying cloud causes the fog to dissipate. 2) For warm advection fog, two layers of low cloud can merge to form deep fog, with the depth exceeding 1000 m, when strong advection of warm moist air produces active thermal-turbulence mixing above the thermal-turbulence interface. 3) Turbulence near the sea surface is mainly thermally driven for cold advection fog, but mechanically driven for warm advection fog. 4) The momentum fluxes of both fog cases are below 0.04 kg m−1 s−2. However, the sensible and latent heat flux differ between the cases: in the cold advection fog case, the sensible and latent heat fluxes are roughly upward, averaging 2.58 and 26.75 W m−2, respectively; however, in the warm advection fog case, the sensible and latent heat flux are mostly downward, averaging −6.98 and −6.22 W m−2, respectively. 5) Low-level vertical advection is important for both fogs, but has a larger influence on fog development in the warm advection fog case.

On the relationship between climatic variables and pressure systems over Saudi Arabia in the winter season

The synoptic circulation over Saudi Arabia is complicated and frequently governed by the effect of large-scale pressure systems. In this work, we used NCEP-NCAR global data to illustrate the relationship between climatic variables and the main pressure systems that affect the weather and climate of Saudi Arabia, and also to investigate the influence of these pressure systems on surface air temperature (SAT) and rainfall over the region in the winter season. It was found that there are two primary patterns of pressure that influence the weather and climate of Saudi Arabia. The first occurs in cases of a strengthening Subtropical High (SubH), a weakening Siberian High (SibH), a deepening of the Icelandic Low (IceL), or a weakening of the Sudanese Low (SudL). During this pattern, the SubH combines with the SibH and an obvious increase of sea level pressure (SLP) occurs over southern European, the Mediterranean, North Africa, and the Middle East. This belt of high pressure prevents interaction between midlatitude and extratropical systems, which leads to a decrease in the SAT, relative humidity (RH) and rainfall over Saudi Arabia. The second pattern occurs in association with a weakening of the SubH, a strengthening of the SibH, a weakening of the IceL, or a deepening of the SudL. The pattern arising in this case leads to an interaction between two different air masses: the first (cold moist) air mass is associated with the Mediterranean depression travelling from west to east, while the second (warm moist) air mass is associated with the northward oscillation of the SudL and its inverted V-shape trough. The interaction between these two air masses increases the SAT, RH and the probability of rainfall over Saudi Arabia, especially over the northwest and northeast regions.

Impact of the North Atlantic Oscillation on the Dipole Oscillation of summer precipitation over the central and eastern Tibetan Plateau

ABSTRACTAn analysis of the spatiotemporal variability in summer precipitation during the period 1961–2010 is presented based on monthly precipitation datasets from 66 meteorological stations in the central and eastern Tibetan Plateau (TP). By applying empirical orthogonal function (EOF) analysis, a strong reversal is found in the variability of summer precipitation between the northeastern and the southeastern TP on the inter‐annual timescale; this reversal is defined as the Dipole Oscillation in summer precipitation over the TP.Our analysis shows that the North Atlantic Oscillation (NAO) greatly controls the Dipole Oscillation in TP summer precipitation by modifying the atmospheric circulation over and around the TP. With the increased stationary wave activity spreading eastward from the North Atlantic to the TP, a pronounced wave train pattern bridges the North Atlantic Ocean and the TP. During the positive phase of the NAO, warm moist air from the oceans around Asia is transported by the southeastern flank of the anticyclonic anomaly over East Asia to the northeastern TP. This northward‐moving warm moist air encounters cold air masses transported by the northwestern flank of the cyclonic anomaly over the northeastern TP. The confluence of the cold and warm air masses subsequently strengthens cumulus convective activities and ultimately results in excessive precipitation over the northeastern TP. Meanwhile, as a cyclonic anomaly sets up over northwestern India and Pakistan, water vapour condenses into precipitation over northwestern India and Pakistan, inhibiting Arabian Sea moisture inflows into the southeastern TP and northeastern India. As a result, a precipitation deficit occurs over the southeastern TP. The opposite scenario occurs during the negative phase of the NAO.

Structure and evolution of a squall line in northern China: A case study

The dynamical, thermodynamical and microphysical structures of convective cells associated with a squall line that occurred on 23 June 2011 in northern China are investigated using observational data and the Regional Atmospheric Modeling System (RAMS). The results suggest that: 1) The squall line appears in the front of the upper-level trough with moderate vertical wind shear at the low levels. 2) The cold pool is formed mainly by rainfall in the initial developing stage. During both the developing and mature stages, the cold pool locates behind the leading edge of the storm. The convergence of the cold air diverged from the cold pool and the warm-moist air transported from the southeast environment is the major mechanism that maintains momentum for the squall line development. Meanwhile, the front-to-rear flow forms systematically in the squall line system. During the dissipation stage, the front-to-rear flow fades away and the air flow passes through the storm at the high level. The cold pool moves ahead of the storm and cuts off the supply of the warm-moist air to the updraft of the storm, leading to demise of the storm. 3) The location of the squall line leading edge is closed to the location where the wind speed and direction at 1km altitude suddenly occurs to be changed. 4) The total warming effect during all the stages processes similar trends of change with height. During the developing stage, the total cooling effect mainly comes from evaporation of cloud water. During the mature and dissipation stages, the melting of hail dominates the total cooling effect in the lower layer. 5) In the developing stage, the growth of hail primarily comes from the processes accreting with raindrops and cloud droplets. During the mature and dissipation stages, the hail particles grow mainly through their accreting with raindrops. Correspondingly, during the initial developing stage, the rainwater comes mainly from cloud water by accreting process near the freezing level. During the mature and dissipation stages, however, the rainwater comes mainly from the melting of hail below the freezing level. The conceptual models of the distribution of the airflow field, cloud microphysical structure and precipitation during the various development stages are presented.

Volcanoes magnify Metro Manila's southwest monsoon rains and lethal floods

Many volcanoes worldwide are located near populated cities that experience monsoon seasons, characterised by shifting winds each year. Because of the severity of flood impact to large populations, it is worthy of investigation in the Philippines and elsewhere to better understand the phenomenon for possible hazard mitigating solutions, if any. During the monsoon season, the change in flow direction of winds brings moist warm air to cross the mountains and volcanoes in western Philippines and cause lift into the atmosphere, which normally leads to heavy rains and floods. Heavy southwest monsoon rains from 18-21 August 2013 flooded Metro Manila (population of 12 million) and its suburbs paralyzing the nation’s capital for an entire week. Called the 2013 Habagat event, it was a repeat of the 2012 Habagat or extreme southwest monsoon weather from 6-9 August, which delivered record rains in the mega city. In both the 2012 and 2013 Habagat events, cyclones, the usual suspects for the delivery of heavy rains, were passing northeast of the Philippine archipelago, respectively, and enhanced the southwest monsoon. Analysis of Doppler data, rainfall measurements, and Weather Research and Forecasting (WRF) model simulations show that two large stratovolcanoes, Natib and Mariveles, across from Manila Bay and approximately 70 km west of Metro Manila, played a substantial role in delivering extreme rains and consequent floods to Metro Manila. The study highlights how volcanoes, with their shape and height create an orographic effect and dispersive tail of rain clouds which constitutes a significant flood hazard to large communities like Metro Manila.

Assessment of condensation of water vapor in the mixing chamber by CFD method

The analyzed topic belongs to the field of design and operation of HVAC systems, focusing mainly on mixing chambers. The paper deals with problems of condensation and freezing of water vapour on walls of mixing chambers in a special case, when the partial pressure of the final resulting state of the mixture of warm moist air and colder air is located above the saturation limit. Experimental in situ methods and computer computational fluid dynamics (CFD) modelling method were used for processing. The main contribution of this work is the finding that partial condensation and freezing of water vapour may occur in local parts of the mixing chamber. It causes problems in terms of hygienic safety and service life of these devices. In particular it has been found that condensation and freezing of water vapour may occur even if relative humidity of the resulting mixture is about 70 %.

δ18O characteristics of meteoric precipitation and its water vapor sources in the Guilin area of China

The stable isotopic composition of meteoric precipitation is an important component of global and regional water cycle research. Stable isotope data can help reconstruct paleoclimate related to ice cores, lake sediments, and stalagmites. We investigated the daily variation in isotopic composition of meteoric precipitation from 2008 to 2012 in the Guilin region of China. δ18O of meteoric precipitation ranged from −14.21 to +2.38 ‰, with an average value of −5.78 ‰ (Vienna Standard Mean Ocean Water; VSMOW). Meteoric precipitation in the summer half-year (May through October) increased, with a relatively low δ18O value of −8.04 ‰ (VSMOW; average of 261 groups) and −56.03 ‰ (VSMOW) of average δD, accounting for 67.6 % of the total annual meteoric precipitation. Meteoric precipitation in the winter half-year (November through April) decreased, with a relatively high δ18O value of −2.89 ‰ (average of 210 groups) and −9.23 ‰ of average δD, accounting for 32.4 % of total meteoric precipitation. The local meteoric water line (LMWL) equation in Guilin area has local climate characteristics. By combining environmental isotope data of precipitation using a backwards trajectory, water vapor sources of the meteoric precipitation in Guilin area are inferred and traced. Our results show that the isotopic composition of meteoric water vapor sources in Guilin area are related to monsoon type, source of precipitation cloud masses, and precipitation properties. The isotopic composition of meteoric precipitation in the summer half-year (May through October) was mainly affected by the summer monsoon or summer typhoons, namely controlled by water vapor source from the Bay of Bengal and the South China sea, and the second the West Pacific, and the δ18O value of meteoric precipitation was strongly negative. There was a significant negative correlation between the δ18O values of meteoric precipitation and the amount of precipitation and temperature in the summer half-year. The amount effect of the meteoric precipitation often concealed the temperature effect. The isotopic composition of meteoric precipitation in the winter season or winter half-year was affected by the water vapor source of the warm moist air masses from the West Pacific and continental cold air masses from the Siberia–Mongolia/winter monsoon or local evaporation vapor circulation, and the δ18O value of meteoric precipitation was relatively positive, and indicated that the water vapor of meteoric precipitation along the water vapor trajectory was affected by the evaporation as well as the local water vapor evaporation. The research results have showed that different sources of water vapor has a significant influence on the δ18O variation of meteoric precipitation, therefore, analysis of δ18O in the meteoric precipitation, especially its seasonal variation characteristics of analysis, can conversely reveal the water vapor sources of local meteoric precipitation.