December, January And February Research Articles

Forecasts of ENSO evolution using spatial–temporal projection model

AbstractEl Niño–Southern Oscillation (ENSO) prediction is one of the most debated and challenging tasks, whilst its real‐time operational prediction skill still has room for improvement. In this study, spatial–temporal projection model is applied to predict Niño3.4 index at lead time of one to six months. By regressing variable fields onto Niño3.4 index month by month, physical‐based predictability sources, that is, the mixed‐layer oceanic temperature, sea surface temperature, thermocline depth, and accumulated westerly‐wind‐events index over the specific regions are detected as the predictors. Based on the temporal evolution of coupled modes of predictors and Niño3.4 index, the Niño3.4 index from JAS (July, August, and September) to DJF (December, January, and February) can be predicted once a year. The model could nicely reproduce the evolution of Niño3.4 index from JAS to DJF. It also achieved high prediction skills for the year‐to‐year DJF Niño3.4 index, with a root‐mean‐square error of 0.46 in the training period (1950–2000) and 0.52 in the independent‐forecast period (2001–2016). Further investigation shows that the forecast is more reliable when the forecasted ENSO amplitude is much larger.

Diurnal cycle of rainfall and convection over the Maritime Continent using TRMM and ISCCP

AbstractThis study investigates the diurnal cycle of rainfall, convection, and precipitation features (PFs) over the Maritime Continent (MC). The study uses Tropical Rainfall Measuring Missions (TRMM) Multi‐satellite Precipitation Analysis (TMPA; product 3b42), TRMM PFs, and convective classifications from the International Satellite Cloud Climatology Project (ISCCP) data. Together, these satellites dataset paint a comprehensive picture of the diurnal cycle of rainfall and convection over the MC consistent with past research. Isolated convection initiates around midday over the higher terrain of the large islands (Java, Borneo, and Papua New Guinea). The convection becomes more organized through the afternoon and evening, leading to peak rainfall over the islands around 1800–2100 local standard time (LST). Over the next few hours, some of that rainfall transitions to stratiform rain over land. The convection then propagates offshore overnight with rainfall peaking along the coast around 0300–0600 LST and then over ocean around 0600–0900 LST. ISCCP data suggests that the overnight and early morning convection is more associated with isolated convective cells than the remnants of mesoscale convective systems. The coastal and oceanic diurnal ranges also seem to be larger in stratiform rainfall, in contrast to land where convective rainfall dominates. Seasonally the diurnal variation of rainfall, convection, and PFs over the region have greater amplitude during DJF (December, January, and February) than JJA (June, July, and August). Given the MC's critical role in the global climate, examining variations in these cycles with respect to the Madden–Julian Oscillation and equatorial waves may ultimately lead to improved subseasonal weather forecasts.

Evaluating the Relationship between Rainfall, Maximum Temperature and Convective Systems over Selected Cities in Nigeria

The convective systems and maximum temperature are key weather parameters that affect various sectors of the Nigerian economy, especially Agriculture, health and transportation. Agriculture which is the mainstay of the economy of Nigeria is weather driven. A balanced weather condition brings about good crop yield which in turn have a positive impact on the economy. The aim of this study was to evaluate the relationship between rainfall, maximum temperature and convective activities over Ikeja, Abuja and Kano cities in Nigeria. Monthly weather data of squall, thunderstorms, maximum temperature and rainfall were obtained from the archives of the Nigeria Meteorological Agency for the period between 1985 and 2015 (30 years). Seasonal and inter-annual variations and relationships between the parameters were analyzed. Over Ikeja the result highlighted a gradual increase in these parameters from January to May/June, while the decrease began from October through to December. Further analysis revealed two separate peak periods for these parameters, with rainfall having its peaks in the months of June and September; Thunderstorm, June and October, and squall attaining its maxima in May and October. Over Kano, March, April and May (MAM) and September, October and November (SON) period indicated that the rain that fell during that period had positive correlation while December, January and February (DJF) and June, July and August (JJA) has a negative correlation. Over Abuja, DJF, MAM and SON showed positive while JJA shows a negative correlation. There will be a need for further studies which will consider the role(s) being played by the various triggering mechanisms and the extent to which the influence of the occurrence of these convective activities rainfall and maximum temperature. The utilization of modelling and mapping techniques may also give further insight into the variation of these systems and a clue to issuing more accurate forecasts and predictions.

Analysis of Java Island’s ozone layer and ultra violet index variability based on satellite data

The ozone layer has a very important role in our atmosphere because it can protect every living on the surface of the earth against harmful Ultra Violet-B radiation. This study aims to discuss and analyze the linkages of ozone layer and Ultra Violet index (UVI) in Java Island and using of FFT to find the period that dominates the ozone layer and UVI variation. The results obtained are characteristic of ozone layer and UVI as well as linkage of UVI to ozone layer in Java Island. Using data of the Ozone Monitoring Instrument (OMI) sensor on AURA satellites from 2005—2016 has been obtained monthly, seasonal and annual characteristics for ozone and UVI and the period dominating the variation of the ozone layer and UVI. The ozone layer varied between 238 DU to 277 DU, the annual variation pattern peaked in October and the minimum in January. The UVI varies between 7.8 and 13.6. The annual variation of UVI peaked in October and the minimum in June. Linear regression of the UVI with ozone in December, January and February (DJF) showed a negative correlation coefficient of 0.77 which means there is a strong correlation between decreasing of ozone concentration with increasing of UVI. Variability of Java Island’s ozone layer is dominated by six month, 12-months and 28-months cycles. While UVI most dominated by the cycle of 6 months and 12 months.

Parameterizing cloud top effective radii from satellite retrieved values, accounting for vertical photon transport: quantification and correction of the resulting bias in droplet concentration and liquid water path retrievals

Abstract. Droplet concentration (Nd) and liquid water path (LWP) retrievals from passive satellite retrievals of cloud optical depth (τ) and effective radius (re) usually assume the model of an idealized cloud in which the liquid water content (LWC) increases linearly between cloud base and cloud top (i.e. at a fixed fraction of the adiabatic LWC). Generally it is assumed that the retrieved re value is that at the top of the cloud. In reality, barring re retrieval biases due to cloud heterogeneity, the retrieved re is representative of smaller values that occur lower down in the cloud due to the vertical penetration of photons at the shortwave-infrared wavelengths used to retrieve re. This inconsistency will cause an overestimate of Nd and an underestimate of LWP (referred to here as the “penetration depth bias”), which this paper quantifies via a parameterization of the cloud top re as a function of the retrieved re and τ. Here we estimate the relative re underestimate for a range of idealized modelled adiabatic clouds using bispectral retrievals and plane-parallel radiative transfer. We find a tight relationship between gre=recloud top/reretrieved and τ and that a 1-D relationship approximates the modelled data well. Using this relationship we find that gre values and hence Nd and LWP biases are higher for the 2.1 µm channel re retrieval (re2.1) compared to the 3.7 µm one (re3.7). The theoretical bias in the retrieved Nd is very large for optically thin clouds, but rapidly reduces as cloud thickness increases. However, it remains above 20 % for τ<19.8 and τ<7.7 for re2.1 and re3.7, respectively. We also provide a parameterization of penetration depth in terms of the optical depth below cloud top (dτ) for which the retrieved re is likely to be representative. The magnitude of the Nd and LWP biases for climatological data sets is estimated globally using 1 year of daily MODIS (MODerate Imaging Spectroradiometer) data. Screening criteria are applied that are consistent with those required to help ensure accurate Nd and LWP retrievals. The results show that the SE Atlantic, SE Pacific and Californian stratocumulus regions produce fairly large overestimates due to the penetration depth bias with mean biases of 32–35 % for re2.1 and 15–17 % for re3.7. For the other stratocumulus regions examined the errors are smaller (24–28 % for re2.1 and 10–12 % for re3.7). Significant time variability in the percentage errors is also found with regional mean standard deviations of 19–37 % of the regional mean percentage error for re2.1 and 32–56 % for re3.7. This shows that it is important to apply a daily correction to Nd for the penetration depth error rather than a time–mean correction when examining daily data. We also examine the seasonal variation of the bias and find that the biases in the SE Atlantic, SE Pacific and Californian stratocumulus regions exhibit the most seasonality, with the largest errors occurring in the December, January and February (DJF) season. LWP biases are smaller in magnitude than those for Nd (−8 to −11 % for re2.1 and −3.6 to −6.1 % for re3.7). In reality, and especially for more heterogeneous clouds, the vertical penetration error will be combined with a number of other errors that affect both the re and τ, which are potentially larger and may compensate or enhance the bias due to vertical penetration depth. Therefore caution is required when applying the bias corrections; we suggest that they are only used for more homogeneous clouds.

South American precipitation changes simulated by PMIP3/CMIP5 models during the Little Ice Age and the recent global warming period

Large climate variations have been detected from paleoclimatic records in some regions of South America during the last 500 years. Among them, the Altiplano and the subtropical Andes regions exhibited wetter‐than‐normal conditions during the 17th century within the paleoclimatic period known as Little Ice Age (LIA). On the other hand, both regions experienced drier‐than‐normal conditions in the second part of the 20th century in association with the recent global warming period (GWP). This study provides an assessment of the ability of four models of the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3)/fifth phase of the Coupled Model Intercomparison Project (CMIP5) experiments in reproducing those regional rainfall changes and the associated large‐scale circulation features.Climate models can represent qualitatively the temperature changes observed in South America in both periods, LIA and GWP, as compared to the control run, but they do not properly describe the associated precipitation changes. However, they can simulate, in some extent, the large‐scale circulation changes that previous works identified as important in driving the precipitation changes in both regions. Therefore, the assessment allows to detect the following changes in LIA (GWP): (a) equatorwards (polewards) displacement of the southern branch of the Hadley cell, in turn associated with wetter (drier) conditions in subtropical south America; (b) negative (positive) upper‐level zonal wind changes related with positive (negative) December, January and February (DJF) rainfall changes in the Altiplano; and (c) positive (negative) low‐level zonal wind changes associated to positive (negative) JJA rainfall changes in the subtropical Andes, being in turn related to hemispheric wind changes resembling a negative (positive) phase of the southern annular mode.

Interannual variations in length of day and atmospheric angular momentum, and their seasonal associations with El Niño/Southern Oscillation-like sea surface temperature patterns

This study examines the seasonal connections between the interannual variations in LOD (length of day)/AAMglobe (the relative atmospheric angular momentum for the whole globe) and the ENSO-like SST (El Nino/Southern Oscillation-like sea surface temperature) pattern and corresponding zonal and vertical circulations. Consistent with previous studies, the ENSO-like SST impact the following season LOD/AAMglobe, with the strongest correlations in DJF (December, January, and February), when it is likely to be the peak El Nino/La Nina period. Lag correlations between the interannual variations in LOD/AAMglobe and surface temperature, and the interannual variations in LOD and both zonal circulation and vertical airflow around the equator, consistently indicate that the LOD/AAMglobe reflect the potential impacts of variations in the Earth’s rotation rate on the following season’s sea surface temperatures (SST) over the tropical central and eastern Pacific (where the ENSO-like SST pattern is located). Moreover, the centers of strongest variation in the AAMcolumn (the relative atmospheric angular momentum for an air column and the unit mass over a square meter) are located over the mid-latitudinal North Pacific in DJF and MAM (March, April, and May), and over the mid-latitudinal South Pacific in JJA (June, July, and August) and SON (September, October, and November). This suggests that the AAMcolumn over the mid-latitudinal Pacific around 30°N (30°S) dominate the modulation of Earth’s rotation rate, and then impact the variations in LOD during DJF and MAM (JJA and SON).

Improving soil organic carbon parameterization of land surface model for cold regions in the Northeastern Tibetan Plateau, China

Most current land surface models (LSMs) show poor performance in soil water and temperature simulations for cold regions because of the inappropriate model structures and ill-parameterizations. This study aims to explore how to parameterize soil organic carbon (SOC) in term of soil moisture simulations using the Community Land Model version 4.0 (CLM4.0) model and the Dynamic Land Model version 1.0 (DLM1.0) model. Firstly, we discuss the sensitivities of modeled soil moisture to SOC based on observations. The SOC parameterizations in both CLM4.0 and DLM1.0 were proved poor against the measured SOC through sensitivity analysis for the Heihe River watershed area (cold but with high SOC). A SOC parameterization was developed and tested based on multiple year observations. Our findings are twofold: (i) the soil organic parameterizations in CLM4.0 and DLM1.0 are inappropriate for simulating soil moisture in cold regions with high SOC, and the modified SOC parameterization significantly improves the soil moisture simulations; (ii) the impacts of SOC on soil moisture vary significantly with seasons, which is largest for JJA (June, July and August) followed by SON (September, October and November), MAM (March, April and May) and DJF (December, January and February). This study highlights that the impacts of SOC should be fully considered for LSMs soil moisture simulations, especially for cold areas with high SOC.

Historical and potential changes of precipitation and temperature of Alberta subjected to climate change impact: 1900–2100

We investigated changes to precipitation and temperature of Alberta for historical and future periods. First, the Mann-Kendall test and Sen’s slope were used to test for historical trends and trend magnitudes from the climate data of Alberta, respectively. Second, the Special Report on Emissions Scenarios (SRES) (A1B, A2, and B1) of CMIP3 (Phase 3 of Coupled Model Intercomparison Project), projected by seven general circulation models (GCM) of the Intergovernmental Panel on Climate Change (IPCC) for three 30 years periods (2020s, 2050s, and 2080s), were used to evaluate the potential impact of climate change on precipitation and temperature of Alberta. Third, trends of projected precipitation and temperature were investigated, and differences between historical versus projected trends were estimated. Using the 50-km resolution dataset from CANGRD (Canadian Grid Climate Data), we found that Alberta had become warmer and somewhat drier for the past 112 years (1900–2011), especially in central and southern Alberta. For observed precipitation, upward trends mainly occurred in northern Alberta and at the leeward side of Canadian Rocky Mountains. However, only about 13 to 22 % of observed precipitation showed statistically significant increasing trends at 5 % significant level. Most observed temperature showed significant increasing trends, up to 0.05 °C/year in DJF (December, January, and February) in northern Alberta. GCMs’ SRES projections indicated that seasonal precipitation of Alberta could change from −25 to 36 %, while the temperature would increase from 2020s to 2080s, with the largest increase (6.8 °C) in DJF. In all 21 GCM-SRES cases considered, precipitation in both DJF and MAM (March, April, and May) is projected to increase, while temperature is consistently projected to increase in all seasons, which generally agree with the trends of historical precipitation and temperature. The SRES A1B scenario of CCSM3 might project more realistic future climate for Alberta, where its water resources can become more critical in the future as its streamflow is projected to decrease continually in the future.

Comparison of versions 6 and 7 3-hourly TRMM multi-satellite precipitation analysis (TMPA) research products

This paper examines differences between Version 6 (V6) and Version 7 (V7) 3-hourly TRMM (Tropical Rainfall Measuring Mission) Multi-Satellite Precipitation Analysis (TMPA 3B42) research products in JJA (June, July and August) and DJF (December, January and February) over a 13-year period from 1998 to 2010 on a global scale. Different surface types and rain regimes are considered in the comparison. The study finds that more rain events are found in V7 than those in V6 in both JJA and DJF, especially over oceans. Overall, both versions show a good agreement in moderate and heavy rain regimes. High Pearson’s correlation coefficients are found in tropical rain band regions. Histograms of both versions are very similar; however higher frequencies of rain events are found in V7 in light rain regime, especially over oceans, than those in V6. For light rain, rainfall estimates in V6 are less than those in V7 over land and oceans in both seasons. For moderate rain, rainfall estimates in V6 are larger than those in V7 over land in most years. Over oceans, it is a mixed situation in which V6>V7 for some years and V6<V7 for the other years. For heavy rain, rainfall estimates in V6 are larger than those in V7 throughout all JJA and DJF seasons for both land and oceans, which is also shown in a case study. Large variance in the individual differences is found in light rain and less in heavy rain. No apparent trends are observed. For light rain, all statistics support that there is an uncertainty issue in both versions.

Seasonal variability of aerosol vertical profiles over east US and west Europe: GEOS-Chem/APM simulation and comparison with CALIPSO observations

In this study, we employed 5years (2007–2011) of the CALIPSO level-3 monthly aerosol extinction product to compare with the GEOS-Chem/APM simulations for the same time period over two major industrial regions (east US and west Europe). The objective is to understand which aerosol types or species significantly determine the vertical profiles by comparing the seasonal variability between the simulations and observations. Our study shows that the model successfully produces the magnitude of aerosol extinction, profile shape, and their seasonal variability observed by CALIPSO over both east US (EUS) and west Europe (WEU). The extinctions below 1km make up 44–79% to the total, from either the model simulations or satellite retrievals, with larger percentages in winter seasons (62–79%) and smaller percentages in summer seasons (44–57%) associated with the strength of vertical transport. The shape of the vertical profiles has, therefore, a distinct seasonal variability, with a more like quasi-exponential shape in DJF (December, January, and February) and SON (September, October, and November) than in MAM (March, April, and May) and JJA (June, July, and August), which have been discerned from both measurements and simulations. Analysis of modeled aerosol species indicates that secondary particles (SP), containing sulfate, ammonia, nitrate, and secondary organic aerosols (SOAs), predominantly determine the total aerosol vertical profiles while black carbon (BC), primary organic carbon (OC), and sea salt (SS), only account for a small fraction and are also limited near the surface. Mineral dust (DS) contributes more to the total extinction over WEU than over EUS, particularly in MAM, a result of being adjacent to the North Africa desert. Secondary inorganic aerosol (SIA, i.e. sulfate, ammonia, and nitrate) contributes most of the total SP mass in DJF and SON while SOA is particularly important in MAM and JJA when the emissions from leafed plants are active. Our study also indicates that, compared to aerosol extinction, the number concentration of particles larger than 10nm (CN10) exhibits a different seasonal variation and vertical profile, but Cloud Condensation Nuclei (CCN) concentration at supersaturation of 0.4% (CCN0.4) presents a consistent seasonal variation and similar vertical profile. Therefore, aerosol extinction could be a good indicator for CCN0.4 with regard to seasonal variations of vertical profiles.

Winter- and summertime continental influences on tropospheric O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; and CO observed by TES over the western North Atlantic Ocean

Abstract. The distributions of tropospheric ozone (O3) and carbon monoxide (CO), and the synoptic factors regulating these distributions over the western North Atlantic Ocean during winter and summer were investigated using profile retrievals from the Tropospheric Emission Spectrometer (TES) for 2004–2006. Seasonal composites of TES retrievals, reprocessed to remove the influence of the a priori on geographical and seasonal structure, exhibited strong seasonal differences. At the 681 hPa level during winter months of December, January and February (DJF) the composite O3 mixing ratios were uniformly low (~45 ppbv), but continental export was evident in a channel of enhanced CO (100–110 ppbv) flowing eastward from the US coast. In summer months June, July, and August (JJA) O3 mixing ratios were variable (45–65 ppbv) and generally higher due to increased photochemical production. The summer distribution also featured a channel of enhanced CO (95–105 ppbv) flowing northeastward around an anticyclone and exiting the continent over the Canadian Maritimes around 50° N. Offshore O3-CO slopes were generally 0.15–0.20 mol mol−1 in JJA, indicative of photochemical O3 production. Composites for 4 predominant synoptic patterns or map types in DJF suggested that export to the lower free troposphere (681 hPa level) was enhanced by the warm conveyor belt airstream of mid-latitude cyclones while stratospheric intrusions increased TES O3 levels at 316 hPa. A major finding in the DJF data was that offshore 681 hPa CO mixing ratios behind cold fronts could be enhanced up to &gt;150 ppbv likely by lofting from the surface via shallow convection resulting from rapid destabilization of cold air flowing over much warmer ocean waters. In JJA composites for 3 map types showed that the general export pattern of the seasonal composites was associated with a synoptic pattern featuring the Bermuda High. However, weak cyclones and frontal troughs could enhance offshore 681 hPa CO mixing ratios to &gt;110 ppbv with O3-CO slopes &gt;0.50 mol mol−1 south of 45° N. Intense cyclones, which were not as common in the summer, enhanced export by lofting of boundary layer pollutants from over the US and also provided a possible mechanism for transporting pollutants from boreal fire outflow southward to the US east coast. Overall, for winter and summer the TES retrievals showed substantial evidence of air pollution export to the western North Atlantic Ocean with the most distinct differences in distribution patterns related to strong influences of mid-latitude cyclones in winter and the Bermuda High anticyclone in summer.

Change‐point alterations of extreme water levels and underlying causes in the Pearl River Delta, China

AbstractIn this paper, the Bayesian model and Lepage test were used to detect change point and to analyse associated statistical properties of high/low water levels in summer (June, July and August (JJA)) and winter (December, January and February (DJF)) months across the PRD (Pearl River Delta). The results indicate that: (1) two time intervals, that is 1979–1981 and 1988–1995, witness abrupt changes of SmH/SmL (summer mean high water level/summer mean low water level). The lower PRD is dominated by increased mean and coefficient of variation (Cv) of SmH. Increased mean but decreased Cv of SmL can be observed in the Mainstem Pearl River; (2) WmL (winter mean low water level) and WmH (winter mean high water level) of about 74% of the total stations have two change points occurred roughly during 1969–1971 and 1993–1995. First change points of WmH are mainly characterized by increased mean and Cv, but decreased mean and increased Cv of WmL can be observed across major parts of the PRD. The driving factors causing abrupt changes of water levels are various. Intensive human activities cannot be ignored, for example in‐channel dredging and reallocation of the streamflow within the river channels due to human‐induced topographical changes of river channel. Different responses of high/low water levels to externally influencing factors and interactions between influencing factors make the alterations of the water levels across the PRD more complicated. The findings of this paper will be helpful for the management of the PRD and human mitigation to natural hazards under the changing environment. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Circulation characteristics over the Himalayas during winter season

¶During winter season, atmospheric systems, which traverse from west to east interact with the Himalayan massif and produce widespread rainfall over North India. In this study, we made an endeavor to examine the mean circulation features and large-scale budgets of kinetic energy, heat and moisture over Himalayas and the adjoining domain for winter season. The time-mean circulation is bifurcated into stable mean and transient eddy parts and examined the mean component of the circulation. The uninitialized daily analyses of European Centre for Medium range Weather Forecasts (ECMWF) for five winter seasons (1986–90) comprising December, January and February (DJF) have been used for the purpose.

Local Meridional Circulation and Deserts

This paper investigates the dry climatology of Sahara and Northwest China deserts from the viewpoint of local meridional circulation with Xie and Arkin rainfall dada and NCAR I NCEP reanalysis data. Results show that there are very dry centers with annual rainfall less than 50 mm over these two deserts while the rainy seasons are very different. In the south part of Sahara desert center and Northwest China desert, over 70% rainfall takes place in June, July and August (JJA). While in the north part of Sahara, rainfall mainly concentrates in December, January and February (DJF). The local biosphere-radiation mechanism proposed by Charney cannot explain the climatology of such very dry centers. Neither can the monsoon-desert mechanism proposed by Rodwell and Hoskins do for the strongest descent center is much more northward than the driest center over Sahara in JJA. From the viewpoint of local meridional circulation, the dryness climatology of Sahara and Northwest China deserts is investigated and compared. It is shown that in DJF, descent of local meridional circulation dominates the two deserts and very dry climate is unavoidable although the relative wet season is weak over the northern part of Sahara due to Mediterranean climate. While in JJA, there is ascent over the two deserts especially over Northwest China. Such ascent can explain the rainy season in south part of Sahara and Northwest China deserts. However, it is the local meridional circulation that takes strong and dry northerly from higher latitudes. The northerly either takes little moisture to the centers or prevents deep and strong convection over the centers. Such local meridional circulation leads to the dry climatology over the two deserts.

SSM/I derived snow water equivalent data: The potential for investigating linkages between snow cover and atmospheric circulation

Relationships between snow cover and atmospheric dynamics are difþcult to isolate because of the complex nature of their interaction. While regional snow cover patterns can be altered radically by a single cyclonic event, the presence or absence of terrestrial snow cover can also greatly influence passing weather systems. A consistent time series of snow cover data, covering an extensive spatial area, at a synoptically sensitive temporal resolution is therefore required to examine potential relationships between surface snow conditions and atmospheric variables. Snow water equivalent (SWE) derived from Special Sensor Microwave/Imager (SSM/I) passive microwave data þts these requirements because of all weather imaging capabilities, broad spatial resolution, wide swath width, and frequent revisit time. The applicability of these data to examining relationships between snow cover and atmospheric dynamics is evaluated in this paper through a comparative study of two winter seasons currently available in the appropriate grid format: December, January and February (DJF) 1988/89 and 1989/90. Five‐day average (pentad) SWE imagery derived from SSM/I brightness temperatures using the Atmospheric Environment Service's (AES) dual channel algorithm is analyzed along with gridded National Meteorological Center (NMC, now National Center for Environmental Prediction, NCEP) atmospheric data. Principal components analysis is used to isolate within variable relationships, while time lagged cross correlation analysis is used to identify between variable relationships. Results indicate that both these data and the methodology show great potential for developing an SWE/atmospheric climatology, although integration of a wet snow indicator, also developed by AES, would strengthen the snow cover product. Further discussion regarding the future use of SSM/I derived SWE data for studying snow cover/atmospheric interaction is also presented.

Indian summer monsoon and the east equatorial pacific sea surface temperature

Abstract A detailed examination has been made of the relationship between the space and time variations of the Indian summer monsoon rainfall and the equatorial eastern‐Pacific sea surface temperature (SST) anomaly in different seasons for the 108‐year period, 1871–1978. There is a strong inverse relationship between the two. The correlation coefficients between All‐India monsoon rainfall and the sea surface temperature anomaly for the concurrent season; June, July and August (JJA) and for the succeeding seasons; September, October and November (SON) and December, January and February (DJF) are consistently and highly significant. Even a random sample of 50 years gave values significant at the 0.1 percent level. The sliding window correlation analysis of 10‐, 20‐ and 30‐year widths indicates that the relationships between All‐India monsoon rainfall and the sea surface temperature anomaly for the concurrent JJA and the succeeding SON and DJF seasons exhibit stability and consistency in significance. For contiguous meteorological sub‐divisions west of longitude 80°E the relationship is highly significant for JJA and for succeeding SON and DJF seasons.