Analysis of Extreme Temperature Variability in Rwanda

The temperature is one of the most important factors in weather and climate forecasting.Studying its behaviour is crucial to understanding climate variability,which could vary spatially and temporally at local,regional,and global scales.Several recent studies on air temperature findings show that the Earth’s near surface air temperature increased between 0.6℃ and 0.8℃ throughout the twentieth century.Using temperature records from ten meteorological stations,this study examined climate variability in Rwanda from the 1930s to 2014.The air temperature data were collected from Meteo Rwanda.Before making the analysis,the authors used software,such as Excel 2007 and INSTAT to control the quality of the raw data.The analysis of maxima and minima indicated that the trends of maximum air temperature were positive and significant at height meteorological stations,whereas the trends for minimum air temperature were found to be at 10 meteorological stations.For all parameters analysed,Kigali Airport meteorological station indicated the higher significance of the trends.The majority of meteorological stations showed an increase in both hot days and nights,confirming Rwanda’s warming over time.The analysis of average seasonal air temperature showed almost similar trends even though not all were significant.This similarity in trends could be attributed to the fact that Rwanda’s short and long dry seasons coincide with rainy seasons.

Analysis of Temperature Trends and Variations in the Arabian Peninsula’s Upper Atmosphere

In this study, the trends of upper-air temperatures are analysed by utilising radiosonde observations for the barometric levels at 700, 500, 300, 200, 150, 100 and 50 hPa from five meteorological stations within the Arabian Peninsula from January 1986 to August 2015. The mean monthly variations of the temperatures at these levels are characterised and established. The magnitudes of the annual trends of the mean temperatures for each site for the selected barometric levels are studied and statistically tested using Mann-Kendall rank statistics at different significance levels. The temperature trends at different pressure levels show that the upper troposphere and lower stratosphere are warming, while the middle troposphere is cooling which is consistent with the findings of other studies. The variations in upper air temperature observed in this study can be attributed to a range of factors, including increasing greenhouse gas concentrations, changes in atmospheric circulation patterns, variations in solar activity, aerosols and volcanic eruptions, and land use and land cover change.

Influence of the NAO on Wintertime Surface Air Temperature over East Asia:Multidecadal Variability and Decadal Prediction

In this paper,we investigate the influence of the winter NAO on the multidecadal variability of winter East Asian surface air temperature(EASAT)and EASAT decadal prediction.The observational analysis shows that the winter EASAT and East Asian minimum SAT(EAmSAT)display strong in-phase fluctuations and a significant 60-80-year multidecadal variability,apart from a long-term warming trend.The winter EASAT experienced a decreasing trend in the last two decades,which is consistent with the occurrence of extremely cold events in East Asia winters in recent years.The winter NAO leads the detrended winter EASAT by 12-18 years with the greatest significant positive correlation at the lead time of 15 years.Further analysis shows that ENSO may affect winter EASAT interannual variability,but does not affect the robust lead relationship between the winter NAO and EASAT.We present the coupled oceanic-atmospheric bridge(COAB)mechanism of the NAO influences on winter EASAT multidecadal variability through its accumulated delayed effect of~15 years on the Atlantic Multidecadal Oscillation(AMO)and Africa-Asia multidecadal teleconnection(AAMT)pattern.An NAO-based linear model for predicting winter decadal EASAT is constructed on the principle of the COAB mechanism,with good hindcast performance.The winter EASAT for 2020-34 is predicted to keep on fluctuating downward until~2025,implying a high probability of occurrence of extremely cold events in coming winters in East Asia,followed by a sudden turn towards sharp warming.The predicted 2020/21 winter EASAT is almost the same as the 2019/20 winter.

Temperature Inversions,Meteorological Variables and Air Pollutants and Their Influence on Acute Respiratory Disease in the Guadalajara Metropolitan Zone,Jalisco,Mexico

The presence of temperature inversions (TI), concentration of air pollutants (AP) and meteorological variables (MV) affect the welfare of the population, creating public health problems (acute respiratory diseases ARDs, among others). The Guadalajara Metropolitan Zone (GMZ) experiences high levels of air pollution, which associated with the presence of temperature inversions and meteorological variations is conducive to the incidence of ARDs in children. The aim of this work is to evaluate the TI, MV, AP and their influence on the ARDs in children under five years in the GMZ from 2003 to 2007. In this period, the moderate and strong TI are the most frequent presenting from November to May. The AP shows a variable behavior during the year and between years, with the highest concentration of particles less than 10 microns (PM10), followed by ozone (O3), nitrogen dioxide (NO2), nitrogen oxides (NOX), carbon monoxide (CO) and sulfur dioxide (SO2), the most affected areas are the southeast of the GMZ. Annual arithmetic mean is 213,510 ± 41,209 ARDs consultations. The most important diseases are acute respiratory infections (98.0%), followed by pneumonia and bronchopneumonia (1.1%), asthma and status asthmaticus (0.5%) and streptococcal pharyngitis and tonsillitis (0.4%). Months with most inquiries were from October to March, mainly in the southeast, south and center of the city, coinciding with high levels of AP. Statistical analysis shows that the TI have significant correlation with ARDs in three years, temperature (Temp) in two, relative humidity (RH) in two, wind speed (WS) in three, wind direction (WD) in two, while that air pollutants NOX and NO2 showed significant correlation with ARDs throughout the period. CO and SO2 showed significance in two years, while the PM10 and O3 in one.

On Multi-Timescale Variability of Temperature in China in Modulated Annual Cycle Reference Frame

The traditional anomaly （TA） reference frame and its corresponding anomaly for a given data span changes with the extension of data length. In this study, the modulated annual cycle （MAC）, instead of the widely used climatological mean annual cycle, is used as an alternative reference frame for computing climate anomalies to study the multi-timescale variability of surface air temperature （SAT） in China based on homogenized daily data from 1952 to 2004. The Ensemble Empirical Mode Decomposition （EEMD） method is used to separate daily SAT into a high frequency component, a MAC component, an interannual component, and a decadal-to-trend component. The results show that the EEMD method can reflect historical events reasonably well, indicating its adaptive and temporally local characteristics. It is shown that MAC is a temporally local reference frame and will not be altered over a particular time span by an exten-sion of data length, thereby making it easier for physical interpretation. In the MAC reference frame, the low frequency component is found more suitable for studying the interannual to longer timescale variability （ILV） than a 13-month window running mean, which does not exclude the annual cycle. It is also better than other traditional versions （annual or summer or winter mean） of ILV, which contains a portion of the annual cycle. The analysis reveals that the variability of the annual cycle could be as large as the magnitude of interannual variability. The possible physical causes of different timescale variability of SAT in China are further discussed.

Variation in Summer Surface Air Temperature over Northeast Asia and Its Associated Circulation Anomalies

This study investigates the interannual variation of summer surface air temperature over Northeast Asia（NEA） and its associated circulation anomalies.Two leading modes for the temperature variability over NEA are obtained by EOF analysis.The first EOF mode is characterized by a homogeneous temperature anomaly over NEA and therefore is called the NEA mode.This anomaly extends from southeast of Lake Baikal to Japan,with a central area in Northeast China.The second EOF mode is characterized by a seesaw pattern,showing a contrasting distribution between East Asia（specifically including the Changbai Mountains in Northeast China,Korea,and Japan） and north of this region.This mode is named the East Asia（EA） mode.Both modes contribute equivalently to the temperature variability in EA.The two leading modes are associated with different circulation anomalies.A warm NEA mode is associated with a positive geopotential height anomaly over NEA and thus a weakened upper-tropospheric westerly jet.On the other hand,a warm EA mode is related to a positive height anomaly over EA and a northward displaced jet.In addition,the NEA mode tends to be related to the Eurasian teleconnection pattern,while the EA mode is associated with the East Asia-Pacific/PacificJapan pattern.

Sub seasonal variations of weak stratospheric polar vortex in December and its impact on Eurasian air temperature

Weak stratospheric polar vortex(WPV)events during winter months were investigated.WPV events were identified as being weakest in December,accompanied by the most dramatic increase in geopotential height over the polar region.After the onset of a December WPV event,the dynamic processes influencing Eurasian temperature can be split into two separate periods.Period I(lag of 0-25 days)is referred to as the stratosphere-troposphere interactions period,as it is mainly characterized by stratospheric signals propagating downwards.In Period I,a stratospheric negative Northern Annular Mode(NAM)pattern associated with the WPV propagates downwards,inducing a negative NAM in the troposphere.The anomalous low centers over the Mediterranean and North Pacific bring cold advection to northern Eurasia,resulting in a north-cold-south-warm dipole pattern over Eurasia.The zero line between negative and positive temperature anomalies moves southwards during days 5-20.Stratospheric cold anomalies at midlatitudes propagate downwards to high latitudes in the troposphere and contribute to the dipole structure.During PeriodⅡ(lag of 25-40 days),as downward signals from the stratosphere have vanished,the dynamic processes mainly take place within the troposphere.Specifically,a wave train is initiated from the North Atlantic region to northern Europe.The propagation of wave activity flux intensifies a cyclonic anomaly over northern Europe,which brings cold advection to Scandinavia and warm advection to central Asia.Therefore,a northwest-cold-southeast-warm dipole structure occupies Eurasia and migrates southeastwards during this period.

Annual and seasonal changes of the air temperature with altitude in the Upper Dades valley, High Atlas, Morocco

The purpose of this study is to determine the size of air temperature changes with altitude in the mountains of the arid zone, on the example of the Upper Dades valley(High Atlas, Morocco). The air temperature change with altitude was determined on the basis of 5 years data from three meteorological stations. The analysis was carried out on an annual and seasonal basis. The annual and daily variations of thermal gradients between pairs of stations were also determined. It was found that the average thermal gradient in the Upper Dades valley was-1.02℃ per 100 m. The highest values of the thermal gradient occur in winter and the lowest in summer. In winter,the thermal gradient was characterized by the greatest variability. Minima of the daily variation of air temperature gradients were observed in early morning hours and maxima around midday. In the lower part of the valley, air temperature inversion frequently developed between 10 AM and 3 PM UTC.The obtained results show high thermal gradients in the mountains of the arid zone, with their annual amplitude increasing in the lower parts of the valley.The instantaneous values of the gradients were significantly modified by the supply of latent heat and the occurrence of dust storms. It has been shown that the advection factor plays an important role in shaping large gradient values. The study contains novel results of thermal gradient measurements in high mountains of arid zone.

Significant Shift of Ambient Night-Time Air Temperature during Rice Growing Season in Major US Rice States

Heat stress studies in rice (Oryza sativa sp.) under extreme weather scenarios generally use constant temperatures to influence the crop responses without relation to actual weather changes. These heat stress studies may have limited implications for future crop yields because elevated temperatures are not based on local temperature fluctuations. This study investigated the night-time air temperature pattern and assessed the status and reliability of available weather station data in four major rice growing states;Arkansas (AR), California (CA), Louisiana (LA) and Texas (TX) using four public weather station databases. Hourly and daily night-time air temperatures from 20:00 to 06:00 were obtained from 1940 to 2018 during the rice growing period. During the 67-year period, a significant increase of 1.12°C and 0.53°C in seasonal night air temperature occurred in CA and AR (P ≤ 0.001) while LA and TX showed minimal to no increase in night air temperature. Across all rice states and years, night air temperature fluctuations ranged between ±0.2°C and ±4°C with the greatest occurred in CA (2.9°C) and AR (4.5°C). Mean night-time air temperature across all states ranged from 22.6°C to 29.5°C with a rate of increase of 0.01°C to 0.02°C per year since 1941. Due to a relatively smaller spatial dataset (from 1941-2018), trend analyses for AR, TX and LA showed modest bias with root mean square errors (RMSE) of 0.5°C to 1.1°C of absolute mean temperature across all locations. Results in this study showed seasonal night-time air temperature change occurred in some major US rice producing states during the last 67-years. This study highlights the need for more weather stations near agricultural farms to reliably derive actual temperature patterns in the rice growing regions.

城市轨道交通车站空调冷冻水系统定温差变供水温度和大温差控制策略转换条件研究

[目的]为实现城市轨道交通车站空调冷冻水系统在定温差变供水温度和大温差两种工况下的整体能耗最低,需对这两种控制策略的转换条件进行研究。[方法]以郑州某城市轨道交通车站为例,基于TRNSYS(瞬时系统模拟程序)建立定温差变供水温度和大温差两种工况下的空调冷冻水系统模型,在满足空调冷冻水系统末端制冷量需求的前提下,分别研究冷冻水温差不变、供水温度为7~12℃,以及供水温度不变、供回水温差为5~10℃时对空调冷冻水系统能耗的影响。[结果及结论]两种控制策略的转换条件为:负荷率小于等于40%时,使用定温差变供水温度控制策略更节能;负荷率大于50%时,更适合采用大温差控制策略。该转换条件不仅能满足车站人员舒适度的要求,还实现了两种控制策略联合调控的目标,最终达到降低空调冷冻水系统整体能耗的目的。

变风量空调系统的优化控制

从变风量末端装置控制、空调机组送风温度控制、空调机组风机转速控制、空调系统新风量控制4个方面介绍了变风量空调系统的优化控制原理。每个方面都从控制目标、控制对象、控制逻辑明确了各控制环节要做什么、如何做好的关键环节。

洁净空调冷水阀门一阶惯性滞后PID独立控制方法

冷水阀门一阶惯性控制偏差项造成洁净空调温湿度控制效果较差。为此,提出洁净空调冷水阀门一阶惯性滞后PID独立控制方法。该方法在考虑室内环境基本信息的条件下,建立环境与冷水阀的一阶惯性滞后模型;计算室内洁净空调温湿度新风量,将其作为洁净空调冷水阀门的温湿度独立控制的约束;利用自适应免疫遗传算法优化PID控制器参数,以此为依据实现洁净空调冷水阀门温湿度的独立控制。实验结果表明,该方法控制效果较好、节能率较高。

多联机在超高标准接待项目中的应用

阐述了某超高标准接待项目暖通空调系统的设计特点,从分析落实业主对该项目的主要设计要求入手,介绍了室内设计参数优化、冷热源方案、系统划分、计算与验算、振动噪声控制、备用性及其他细部设计;重点介绍了三管制热回收高显热多联机+直膨式恒温恒湿新风机组+地暖方案在该项目中的应用,为超高标准接待项目及温湿度独立控制空调系统的设计提供了新的解决思路和案例。

基于仿生树形相变循环散热技术研究及变频空调应用

伴随环境温度升高,空调制冷量需求也会逐步增高,从而引发变功率模块发热严重,导致其内部芯片无法良好散热。通常采用压缩机降频工作方法保证电控板安全,但该方法的缺点是温度越高,空调制冷能力越差。针对该缺点,提出一种仿生树形的单向相变循环传热方法,开发了一款单向循环相变风冷散热器,通过焓差室测试,实现了散热器进风口温度62℃时,变频功率模块温度可以降低8℃以上,防止压缩机强制降频造成制冷量衰减。

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（Sub H）, a weakening Siberian High（Sib H）, a deepening of the Icelandic Low（Ice L）, or a weakening of the Sudanese Low（Sud L）. During this pattern, the Sub H combines with the Sib H 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 Sub H, a strengthening of the Sib H, a weakening of the Ice L, or a deepening of the Sud L. 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 Sud L 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.

Intraseasonal Variability of Summertime Surface Air Temperature over Mid-High-Latitude Eurasia and Its Prediction Skill in S2S Models

Features of the dominant modes of surface air temperature(SAT)on the intraseasonal timescale over the mid-highlatitude Eurasia(MHE)during boreal summer(June-September)are investigated based on the ERA5 reanalysis data from 1979 to 2016.The intraseasonal variability(ISV)of SAT over MHE is primarily characterized by an eastward propagation along 60°N,which is found to impact the regional weather in China,including summertime extreme hot and cool events.The forecast skill and potential predictability of the ISV of SAT over MHE are assessed for 5 dynamical models that have participated in the subseasonal-to-seasonal(S2 S)prediction project,by analyzing12 years’(1999-2010)model reforecast/hindcast data.By using the principal component(PC)index of the leading intraseasonal SAT modes as a predictand,we found that the forecast skill for ISV of SAT can reach out to 11-17 days,and the ECMWF model exhibits the best score.All the S2 S models tend to show 1)a relatively higher skill for strong intraseasonal oscillation(ISO)cases,2)a systematic underestimate of the amplitude of the SAT ISV signal,and 3)different skills during different phases of ISO cases.Analysis of potential predictability based on the perfectmodel assumption reveals a 4-6-day skill gap for most models,and the skill gap also varies among different phases of ISO events.The results imply the need for continued development of operational forecasting systems to improve the actual prediction skills for the ISV of SAT over MHE.

ENSO对中国东部前后冬天气尺度气温变率的不同影响及其可能机制

基于中国国家气象信息中心提供的中国第一代全球大气和陆面再分析产品(CRA)的逐日气温资料、美国国家海洋和大气管理局(NOAA)重建的逐月海表温度资料以及美国国家环境预报中心/国家大气研究中心(NCEP/NCAR)提供的大气环流再分析资料,研究了厄尔尼诺-南方涛动(ENSO)对中国东部前、后冬天气尺度气温变率的影响及其物理机制。结果表明,ENSO对中国东部天气尺度气温变率的影响在前、后冬存在显著差异。ENSO对前冬中国东部天气尺度气温变率影响较弱,后冬则显著增强。后冬时期,ENSO与长江中下游地区天气尺度气温变率呈现显著正相关,即厄尔尼诺年后冬天气尺度气温变率增强,气温波动幅度增大;拉尼娜年后冬天气尺度气温变率减弱,气温变化较为平缓。ENSO在后冬可通过影响与欧亚大陆上空南北温度梯度相关的大气斜压性调节下游东亚地区大气环流的天气尺度变率,进而影响天气尺度气温变率。厄尔尼诺年后冬,南北温度梯度大,大气斜压性较强,经向风活跃,冷空气活动较为频繁,天气尺度气温变率增大;拉尼娜年后冬,异常情况与之大致相反。在前冬ENSO对欧亚大陆上空南北梯度即大气斜压性影响较小,因而对中国东部天气尺度气温变率的影响也较弱。本研究的成果丰富了对ENSO影响中国气温变率的理解,有利于中国冬季气温季节预测水平的提升。

南极磷虾变温热风干燥工艺研究

为探索一种南极磷虾变温热风干燥工艺,以干燥时间、蛋白质、脂肪、虾青素含量为指标,研究第一段干燥温度、第二段干燥温度、水分含量节点对南极磷虾干燥效果的影响,采用多指标综合评分法评价干燥效果,在单因素实验基础上,采用正交试验优化南极磷虾干燥工艺条件。结果表明,南极磷虾变温热风干燥最佳工艺条件为第一段干燥温度55℃,第二阶段干燥温度85℃,水分含量节点50%。此优化工艺条件下得到的干制南极磷虾蛋白质、脂肪、虾青素含量和干燥时间分别为69.24%、19.79%、232.72μg/g、300 min,干燥效果综合评分为99.05。

基于冷气预冷技术的高马赫数涡轮发动机建模与仿真研究

针对高马赫数涡轮发动机存在的涡轮部件热防护问题,以基于冷气预冷(CCA)技术的变循环涡扇发动机为例,通过建立燃油的热物性库、电动燃油泵和空气-燃油换热器的计算模型,改进燃烧室和涡轮的计算模型,发展了可控制涡轮叶片温度的变引气量整机性能计算模型。结果表明,在Ma3,20.9km的设计点,采用CCA技术能够将涡轮引气温度降低181K,相对引气量降低22.04%,并使推力和比冲分别提高2.03%,0.66%;在Ma3的节流状态下,控制涡轮叶片温度的发动机推力随转速降低而减小得更快,但是使空气-燃油换热器空气侧的温降最高达到240K,且总压损失明显降低;沿飞行轨迹,控制涡轮叶片温度的发动机在飞行马赫数大于1.8具有更大的推力,在飞行马赫数小于1.8具有更高的比冲。空气-燃油换热器在发动机最大热负荷状态的性能设计是影响引气温降和涡轮引气回流裕度的关键。

变流量空气源热泵集中供暖系统水泵及末端控制方法研究

本文建立了变流量空气源热泵建筑供暖的数学模型,利用该模型研究了不同水泵控制方式下空气源热泵系统的性能。结果表明:为了使热泵机组保持较高的性能,其最小经济流量为额定流量的30%;3种控制方式中,供回水干管压差控制水泵功耗最大,最不利末端支路压差控制水泵功耗最小;相比于供回水干管压差控制,最不利末端支路压差控制水泵可节能0~31.84%;3种控制方式中,温差控制系统总功耗始终最大,最不利末端压差控制最小,它们的差值平均值在高负荷率下达到6.20%;压差控制和温差控制均可满足建筑供暖需要,但压差控制室内温度波动更小,适合用于对室内温度要求较高的场所。