Interannual and intraseasonal variations of the energy budget over the polar regions and its climatic implications

The atmospheric energy budget is often adopted by previous studies to explore the balance between energy sources/sinks and the divergence of atmospheric energy flux. Because the atmospheric circulation is essentially generated by the energy balance between sources and sinks, a better knowledge of an energy budget will lead to a better understanding of the atmospheric circulation and its variations.;Climatologically, the polar regions are the major sink regions of global energy. The energy in the polar regions undergoes interannual and 30-60 day variations. It was inferred from previous studies dealing with the poleward propagation of angular momentum that energy exhibits a propagating signature, originating from the tropics and extending into the polar regions, on the interannual and 30-60 day timescales. To gain a new perspective on the polar energy change, the polar energy budget was studied in this thesis, based on a hypothesis that the low-latitude atmospheric energy with poleward propagation could indirectly affect the divergence of energy flux, and, in turn, affect the variations of the polar energy budget. In addition, polar climate changes (e.g., precipitation) associated with the energy propagation were also studied.;Results indicated that the energy changes in the polar regions and the tropics are remotely linked through the poleward propagation of energy relay carried out by different types of circulation patterns at different latitudes, as the propagation of angular momentum depicted by previous studies. Analyses have pointed out that the propagation of energy is led by the divergence of energy flux with a horizontal quadrature shift between the former and the latter. After a larger (smaller) energy propagates into the polar regions, the polar energy budget is changed by an increase (decrease) of energy transport into the polar regions. On the other hand, it was found that the increase (decrease) of energy flux converging into the polar regions is balanced by an increase (decrease) of downward surface flux and upward radiation flux at the top of the atmosphere over the polar regions. Associated with this energy balance, the polar climate changes include a reduced (increased) precipitation and an increased (reduced) outgoing longwave radiation. Maintenance of these changes were discussed

Indian Monsoon Depression: Climatology and Variability

The monsoon climate is traditionally characterized by large amount of seasonal rainfall and reversal of wind direction (e.g., Krishnamurti 1979). Most importantly this rainfall is the major source of fresh water to various human activities such as agriculture. The Indian subcontinent resides at the core of the Southeast Asian summer monsoon system with the monsoon trough extended from northern India across Indochina to the Western Tropical Pacific (WTP). Large fraction of annual rainfall occurs during the summer monsoon season, i.e., June – August1, with two distinct maxima. One is located over the Bay of Bengal with rainfall extending northwestward into eastern and central India, and the other along the west coast of India where the lower level moist wind meets the Western Ghat Mountains (Saha and Bavardeckar 1976). The rest of the Indian subcontinent receives relatively less rainfall.https://digitalcommons.usu.edu/modern_climatology/1001/thumbnail.jp

Pakistan’s two-stage monsoon and links with the recent climate change

Meteorological conditions related to the Pakistan floods of 2010 were examined in the context of monsoon dynamics and large‐scale circulations. Case and climatological analyses suggest that summer precipitation in northern Pakistan comprises two distinct phases: (1) a premonsoon trough phase (July) whose rainfall is more episodic and intense, occurring prior to arrival of the monsoon trough, and (2) a monsoon trough phase (August) whose rainfall is persistent, yet less episodic, driven by northward migration of the monsoon trough. Analyses of conditional instability, moisture flux, and circulation features support a persistent increase in conditional instability during the July premonsoon trough phase, accompanied by increased frequency of heavy rainfall events. Conversely, evidence does not support intensification of the August monsoon trough phase. The increased convective activity during the premonsoon trough phase agrees with the projected increase in the intensity of heavy rainfall events over northern Pakistan. Largescale circulation analysis reveals an upper‐level cyclonic anomaly over and to the west of Pakistan–a feature empirically associated with weak monsoon. The analysis also suggests that the anomalous circulation in 2010 is not sporadic but rather is part of a long‐term trend that defies the typical linkage of strong monsoons with an anomalous anticyclone in the upper troposphere

Future Changes in Propagating and Non-Propagating Diurnal Rainfall Over East Asia

The characteristics of diurnal rainfall in the East Asian continent consist of a propagating regime over the Yangtze River and a non-propagating regime in southeast China. Simulations of these two diurnal rainfall regimes by 18 CMIP5 models were evaluated from the historical experiment of 1981–2005. The evaluation led to the identification of one model, the CMCC-CM that replicated the key characteristics of diurnal rainfall regimes including the propagation of moisture convergence. Using the CMCC-CM to assess the future (2076–2100) change of diurnal evolution and propagation projected by the RCP4.5 experiment, it was found that propagating diurnal rainfall will enhance and expand southward into the non-propagating regime in southeast China. This change in diurnal rainfall is attributed to the intensification of diurnal land–sea thermal contrast over eastern China and the southward shift of the upper-level jet stream over 20°–30°N. Similar projected changes in diurnal rainfall and associated large-scale dynamical mechanisms were also depicted by four other models (GFDL-ESM2G, GFDL-ESM2M, MRI-CGCM3, and MRI-ESM1) showing a higher skill in representing the diurnal rainfall regimes over East Asia. If such model projection holds true, southeast China will experience an increase in the eastward propagating diurnal rainfall, which could further impact Taiwan

Interannual Variation of Springtime Biomass Burning in Indochina: Regional Differences, Associated atmospheric dynamical changes, and downwind impacts

During March and April, widespread burning occurs across farmlands in Indochina in preparation for planting at the monsoon onset. The resultant aerosols impact the air quality downwind. In this study, we investigate the climatic aspect of the interannual variation of springtime biomass burning in Indochina and its correlation with air quality at Mt. Lulin in Taiwan using long-term (2005–2015) satellite and global reanalysis data. Based on empirical orthogonal function (EOF) analysis, we find that the biomass burning activities vary with two geographical regions: northern Indochina (the primary EOF mode) and southern Indochina (the secondary EOF mode). We determine that the variation of biomass burning over northern Indochina is significantly related with the change in aerosol concentrations at Mt. Lulin. This occurs following the change in the so-called India-Burma Trough in the lower and middle troposphere. When the India-Burma Trough is intensified, a stronger northwesterly wind (to the west of the trough) transports the dryer air from higher latitude into northern Indochina, and this promotes local biomass burning activities. The increase in upward motion to the east of the intensified India-Burma Trough lifts the aerosols, which are transported toward Taiwan by the increased low-level westerly jet. Further diagnoses revealed the connection between the India-Burma Trough and the South Asian jet\u27s wave train pattern as well as the previous winter\u27s El Niño–Southern Oscillation phase. This information highlights the role of the India-Burma Trough in modulating northern Indochina biomass burning and possibly predicting aerosol transport to East Asia on the interannual time scale

Synchronous right hepatectomy and cesarean section in a pregnant lady with hepatocellular carcinoma

AbstractINTRODUCTIONCancer in pregnancy is rare and hepatocellular carcinoma (HCC) during pregnancy is even rarer. Due to limited experience, management of these patients remains challenging.PRESENTATION OF CASEA 33-year old pregnant lady presented with HCC at 28 weeks of gestation. She underwent synchronous cesarean section and right hepatectomy at 32 weeks of gestation. The post-operative course was uneventful. She was discharged home on day 10 after surgery. Histolopathology confirmed HCC. The surgical resection margins were clear. At a follow-up of 3 months after surgery, the mother was disease free and the infant was well.DISCUSSIONHCC during pregnancy is extremely rare. The experience in its management and outcomes are lacking. In managing any patient diagnosed with a malignant neoplasm in pregnancy, both the mother and the fetus have to be considered.CONCLUSIONWith adequate preoperative assessment and a good management strategy, good results can be obtained for both the mother and the baby for a pregnant patient with HCC

An East Asian Cold Surge: Case Study

Since a cold surge is a hazardous weather phenomenon in east Asia, the rapid population increase and economic growth over the past two decades require improvement in forecasting cold surges and their related weather events over this region. However, without a better understanding of these events, this task cannot be accomplished. A cold surge with a well-defined cold front passing through Taiwan was selected to illustrate its impact on the east Asian weather system. This case is typical of a large portion of surges occuring in the region. Major findings of this study are as follows. Coupling with the upper ridge-trough structures of the wave train straddling the eastern seaboard of northeast Asia, cold surges occur sequentially. A cold front with a prefront high pressure zone is formed by the new surge outflow interacting with the anticyclone of the aging surge. The warm moist air advected northeastward along the cold front assists the development of the new surge's low center, while the prefront high pressure zone facilitates the formation of a double-cell structure in the local Hadley circulation. The southeastward propagation of the cold front is driven by the eastward-propagating short-wave trough through the couplets of both new and aging cold surges. The surface weather conditions in the low-elevation zones of Taiwan are modulated by the cold surge flow, but the high-elevation areas may be affected instead by the tropical southeast Asian high. Despite the success of the prior and post-WMONEX (Winter Monsoon Experiment) research in exploring the tropical-midlatitude interaction, the close interaction of cold surges with local weather systems and the planetary-scale circulation in east Asia, illustrated by the case study presented, provides another dimension of cold surge research.This article is from Monthly Weather Review 130 (2002): 2271, doi: 2.0.CO;2" target="_blank">10.1175/1520-0493(2002)1302.0.CO;2. Posted with permission.</p