Variability and trend of the north west Australia rainfall: observations and coupled climate modeling

Since 1950, there has been an increase in rainfall over North West Australia (NWA), occurring mainly during the Southern Hemisphere (SH) summer season. A recent study using 20th century multi-member ensemble simulations in a global climate model forced with and without increasing anthropogenic aerosols suggests that the rainfall increase is attributable to increasing Northern Hemisphere aerosols. The present study investigates the dynamics of the observed trend toward increased rainfall and compares the observed trend with that generated in the model forced with increasing aerosols. We find that the observed positive trend in rainfall is projected onto two modes of variability. The first mode is associated with an anomalously low mean sea level pressure (MSLP) off NWA instigated by the enhanced sea surface temperature (SST) gradients towards the coast. The associated cyclonic flows bring high moisture air to northern Australia, leading to an increase in rainfall. The second mode is associated with an anomalously high MSLP over much of the Australian continent; the anticyclonic circulation pattern with northwesterly flows west of 130°E and generally opposite flows in northeastern Australia, determine that when rainfall is anomalously high, west of 130oE, rainfall is anomalously low east of this longitude. The sum of the upward trends in these two modes compares well to the observed increasing trend pattern. The modeled rainfall trend, however, is generated by a different process. The model suffers from an equatorial cold-tongue bias: the tongue of anomalies associated with El Niño-Southern Oscillation extends too far west into the eastern Indian Ocean. Consequently, there is an unrealistic relationship in the SH summer between Australian rainfall and eastern Indian Ocean SST: the rise in SST is associated with an increasing rainfall over NWA. In the presence of increasing aerosols, a significant SST increase occurs in the eastern tropical Indian Ocean. As a result, the modeled rainfall increase in the presence of aerosol forcing is accounted for by these unrealistic relationships. It is not clear whether, in a model without such defects, the observed trend can be generated by increasing aerosols. Thus, the impact of aerosols on Australian rainfall remains an open question

A comprehensive analysis of coherent rainfall patterns in China and potential drivers. Part I: interannual variability

Interannual rainfall variability in China affects agriculture, infrastructure and water resource management. To improve its understanding and prediction, many studies have associated precipitation variability with particular causes for specific seasons and regions. Here, a consistent and objective method, Empirical Orthogonal Teleconnection (EOT) analysis, is applied to 1951–2007 high-resolution precipitation observations over China in all seasons. Instead of maximizing the explained space–time variance, the method identifies regions in China that best explain the temporal variability in domain-averaged rainfall. The EOT method is validated by the reproduction of known relationships to the El Niño Southern Oscillation (ENSO): high positive correlations with ENSO are found in eastern China in winter, along the Yangtze River in summer, and in southeast China during spring. New findings include that wintertime rainfall variability along the southeast coast is associated with anomalous convection over the tropical eastern Atlantic and communicated to China through a zonal wavenumber-three Rossby wave. Furthermore, spring rainfall variability in the Yangtze valley is related to upper-tropospheric midlatitude perturbations that are part of a Rossby wave pattern with its origin in the North Atlantic. A circumglobal wave pattern in the northern hemisphere is also associated with autumn precipitation variability in eastern areas. The analysis is objective, comprehensive, and produces timeseries that are tied to specific locations in China. This facilitates the interpretation of associated dynamical processes, is useful for understanding the regional hydrological cycle, and allows the results to serve as a benchmark for assessing general circulation models

Losses of phosphorus, potassium and nitrogen from horse manure left on the ground

In this five-month Swedish field study, we examined losses of nutrients from horse manure over time, in order to examine how regularly manure should be cleared from paddocks in order to minimise the risk of nutrient leaching. Small heaps of manure (400 g) were placed in open cylinders outdoors and samples (five replicates) were taken on 12 occasions from December 2020 to May 2021. The samples were analysed for weight, dry matter content and concentrations of total nitrogen (N), ammonium N, total phosphorus (P), water-extractable P (WEP), potassium (K) and carbon (C). There was a fast decline in P and K concentrations and a strong correlation between accumulated precipitation and losses from the manure into the soil. The mean reduction in total-P was 11 mg P kg-1 manure dry weight per mm accumulated precipitation. Manure N was retained in the manure over the five-month period. In conclusion, this study demonstrated high mobility of P and K, indicating a need for strategies for rapid removal of manure from paddocks. Daily removal of manure from paddocks used year-round would, approximately, save 1.7 kg P and 5.5 kg K per horse per year, which could be recycled to replace non-renewable mineral fertilisers

Large and seasonally varying biospheric CO₂ fluxes in the Los Angeles megacity revealed by atmospheric radiocarbon

Measurements of Δ¹⁴C and CO₂ can cleanly separate biogenic and fossil contributions to CO₂ enhancements above background. Our measurements of these tracers in air around Los Angeles in 2015 reveal high values of fossil CO₂ and a significant and seasonally varying contribution of CO₂ from the urban biosphere. The biogenic CO₂ is composed of sources such as biofuel combustion and human metabolism and an urban biospheric component likely originating from urban vegetation, including turf and trees. The urban biospheric component is a source in winter and a sink in summer, with an estimated amplitude of 4.3 parts per million (ppm), equivalent to 33% of the observed annual mean fossil fuel contribution of 13 ppm. While the timing of the net carbon sink is out of phase with wintertime rainfall and the sink seasonality of Southern California Mediterranean ecosystems (which show maximum uptake in spring), it is in phase with the seasonal cycle of urban water usage, suggesting that irrigated urban vegetation drives the biospheric signal we observe. Although 2015 was very dry, the biospheric seasonality we observe is similar to the 2006–2015 mean derived from an independent Δ¹⁴C record in the Los Angeles area, indicating that 2015 biospheric exchange was not highly anomalous. The presence of a large and seasonally varying biospheric signal even in the relatively dry climate of Los Angeles implies that atmospheric estimates of fossil fuel–CO₂ emissions in other, potentially wetter, urban areas will be biased in the absence of reliable methods to separate fossil and biogenic CO₂

Large and seasonally varying biospheric CO₂ fluxes in the Los Angeles megacity revealed by atmospheric radiocarbon

Measurements of Δ¹⁴C and CO₂ can cleanly separate biogenic and fossil contributions to CO₂ enhancements above background. Our measurements of these tracers in air around Los Angeles in 2015 reveal high values of fossil CO₂ and a significant and seasonally varying contribution of CO₂ from the urban biosphere. The biogenic CO₂ is composed of sources such as biofuel combustion and human metabolism and an urban biospheric component likely originating from urban vegetation, including turf and trees. The urban biospheric component is a source in winter and a sink in summer, with an estimated amplitude of 4.3 parts per million (ppm), equivalent to 33% of the observed annual mean fossil fuel contribution of 13 ppm. While the timing of the net carbon sink is out of phase with wintertime rainfall and the sink seasonality of Southern California Mediterranean ecosystems (which show maximum uptake in spring), it is in phase with the seasonal cycle of urban water usage, suggesting that irrigated urban vegetation drives the biospheric signal we observe. Although 2015 was very dry, the biospheric seasonality we observe is similar to the 2006–2015 mean derived from an independent Δ¹⁴C record in the Los Angeles area, indicating that 2015 biospheric exchange was not highly anomalous. The presence of a large and seasonally varying biospheric signal even in the relatively dry climate of Los Angeles implies that atmospheric estimates of fossil fuel–CO₂ emissions in other, potentially wetter, urban areas will be biased in the absence of reliable methods to separate fossil and biogenic CO₂

Oceanic influence on southernmost South American precipitation

The potential oceanic influence on southernmost South American precipitation since 1930 is analyzed in this study. The aim is to define oceanic characteristics that can produce wetter or drier conditions over the mentioned region on different time scales. Results suggest important precipitation-oceanic links in decadal and interdecadal oscillations. The eastern and central subtropical Indian, western tropical Pacific and western and central subtropical Pacific could be forcing the precipitation on decadal time scale. Moreover, the eastern tropical and western subtropical Indian and western and central subtropical Pacific could be forcing the variability of precipitation on interdecadal time scale. Although the research was focused in forcing of precipitation, relations among different regions of the Indian and Pacific oceans on decadal and interdecadal time scales have also been detected. Therefore, results presented here can be useful in describing new aspects of the remote influence of both oceans on regional climate.En este trabajo se analiza la posible influencia oceánica en la variabilidad de la precipitación sobre el extremo sur de Sudamérica desde 1930. El objetivo es definir características oceánicas que pueden producir condiciones de más o menos lluvia en diferentes escalas de tiempo en la mencionada región. Los resultados sugieren importantes relaciones entre los océanos y la precipitación en oscilaciones decadales e interdecadales. El este y centro del índico subtropical, el oeste del Pacífico tropical y el oeste y centro del Pacífico subtropical podrían estar influenciando la precipitación en escala decadal. Por otra parte, la región este tropical y oeste subtropical del índico, y el oeste y centro del Pacífico subtropical podrían influenciar la variabilidad de la precipitación en escala interdecadal. Si bien el estudio se enfocó en la variabilidad de la precipitación, relaciones entre diferentes regiones de los océanos Índico y Pacífico en escalas decadal e interdecadal han sido también detectadas. Por lo tanto, los resultados aquí presentados pueden también ser útiles para describir nuevos aspectos de la influencia remota de ambos océanos en el clima regional.Fil: Berman, Ana Laura. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Silvestri, Gabriel Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmosfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmosfera; ArgentinaFil: Compagnucci, Rosa Hilda. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Velasco Herrera, Victor. Universidad Nacional Autónoma de México. Instituto de Geofísica; Méxic

Relationship between winter orographic precipitation with synoptic and large-scale atmospheric circulation: The case of mount Olympus, Greece

Στην παρούσα εργασία εξετάζονται οι σχέσεις μεταξύ της ατμοσφαιρικής κυκλοφορίας και της χειμερινής (Δεκέμβριος – Μάρτιος) βροχόπτωσης στην περιοχή του Ολύμπου. Απώτερος σκοπός της εργασίας είναι η αξιολόγηση της επίδρασης του ορεινού όγκου του Ολύμπου στη χωρική κατανομή της βροχόπτωσης σε μία μικρής έκτασης περιοχή (100 x 100km2) κατά τη χειμερινή περίοδο. Η εργασία βασίζεται σε βροχομετρικά δεδομένα από 8 σταθμούς, που βρίσκονται περιμετρικά του Ολύμπου, σε υψόμετρα μεταξύ 30 και 1150 μέτρων για την περίοδο μεταξύ 1981 και 2000. Η πολυετής μεταβλητότητα της χειμερινή βροχόπτωσης περιγράφεται από τις συνοπτικές συνθήκες της ατμοσφαιρικής πίεσης στη στάθμη της θάλασσας και από τα γεωδυναμικά ύψη στα επίπεδα των 850 hPa and 500 hPa, αντίστοιχα. Τα συστήματα υψηλής ατμοσφαιρικής πίεσης στην περιοχή της Μεσογείου, μεταξύ των δεκαετιών 1980 και 1990, συνδέονται με τις ελάχιστες τιμές χειμερινής βροχόπτωσης στην περιοχή του Ολύμπου κατά τη διάρκεια των παρατηρήσεων. Το χειμώνα του 1996, η προσθαλάσσια πλευρά του Ολύμπου χαρακτηρίστηκε από πολύ υψηλές τιμές χειμερινής βροχόπτωσης, οι οποίες συνδέονται με μία αυλώνα χαμηλών πιέσεων πάνω από τη Δυτική Μεσόγειο, αλλά και από αυξημένες τροποσφαιρικές υφέσεις στη νότια Αδριατική και το Ιόνιο Πέλαγος. Αυτός ο τύπος της ατμοσφαιρικής κυκλοφορίας δημιουργεί μία ροή αέρα νοτιοανατολικής διεύθυνσης στο Αιγαίο, η οποία επηρεάζει περισσότερο (λιγότερο) τη χειμερινή βροχόπτωση στην προσθαλάσσια (ηπειρωτική) πλευρά του Ολύμπου. Εν αντιθέσει, η επικράτηση υφέσεων στην κεντρική Μεσόγειο και πάνω από τον Κόλπο της Γένοβας, δημιουργεί ατμοσφαιρική κυκλοφορία νότιας / νοτιοδυτικής διεύθυνσης και επηρεάζει περισσότερο τη χειμερινή βροχόπτωση στην ηπειρωτική πλευρά του Ολύμπου (r= -0.80, Σταθμός Ελασσόνας) και λιγότερο την προσθαλάσσια πλευρά του Ολύμπου (r= -0.67; Σταθμός Κατερίνης). Η κατάσταση αυτή τονίζει την επίδραση του ορεινού όγκου του Ολύμπου στην κατανομή της χειμερινής βροχόπτωσης, με μεγάλες παρατηρούμενες διαφορές μεταξύ της ηπειρωτικής και προσθαλάσσιας πλευράς. Μεγάλης κλίμακας φαινόμενα, όπως η ταλάντωση του Βόρειου Ατλαντικού ή του Αρκτικού, επηρεάζουν περισσότερο τη χειμερινή βροχόπτωση στην ηπειρωτική πλευρά του Ολύμπου.The relationship between the winter (DJFM) precipitation and the atmospheric circulation patterns is examined around Mount Olympus, Greece in order to assess the effects of orography and atmospheric dynamics over a small (less than 100 x 100 km) spatial domain. Winter accumulated rainfall datasets from 8 stations spread along the eastern (marine) and western (continental) sides of the Mount Olympus at elevations between 30 m and 1150 m are used during the period 1981 to 2000. Synoptic scale conditions of mean sea-level pressure and geopotential heights at 850 hPa and 500 hPa, were used to explain the multiyear rainfall variability. High pressure systems dominated over the central Mediterranean and most parts of central Europe during the late 1980’s and early 1990’s, are associated with minimum winter rainfall along both sides of Mount Olympus. The winter of 1996 was associated with peak in rainfall along the marine side of the mountain and was characterized by enhancement of upper level trough over the western Mediterranean and increased low tropospheric depressions over the southern Adriatic and the Ionian Seas. This atmospheric circulation pattern facilitated a southeasterly air flow that affected more (less) the marine (continental) sides of the mountain. In contrast, dominance of low pressure systems with cores over the Gulf of Genoa and the Central Mediterranean affect the study area mostly from west/southwest revealing higher correlations with the precipitation in the continental side of the mountain (r= -0.80; Elassona station) and considerably lower correlations with the marine side (r = -0.67; Katerini station). This highlights the orographic barrier of the Mount Olympus revealing large differences between the upward and leeward sides. Large scale atmospheric patterns like the North Atlantic Oscillation and the Arctic Oscillation seem to influence the winter rainfall in the lowlands along the continental side of the mountain

Rainfall Prediction Using Teleconnection Patterns Through the Application of Artificial Neural Networks

All aspects of human life are, directly or indirectly, affected by climatic processes. This effect is especially noticeable in such fields as agriculture, irrigation, economy, telecommunications, transportation, traffic, air pollution and military industries (Haltiner & Williams 1980). A number of researchers have studied the possibility of forecasting rainfall several months in advance using climate indices such as SOI, PDOI and NPI (e.g. Silverman and Dracup 2000). A well-known atmospheric phenomenon is the Southern Oscillation (SO). The SO is an atmospheric see-saw process in the tropical Pacific sea level pressure between the eastern and western hemispheres associated with the El Niño and La Niña oceanographic features. The oscillation can be characterized by a simple index, the Southern Oscillation Index (SOI). (Kawamura et al., 1998). The Pacific Decadal Oscillation index (PDOI) is the leading principal component of monthly sea surface temperature (SST) anomalies in the North Pacific Ocean north of 20°N (Zhang et al., 1997; Mantua et al., 1997). Trenberth and Hurrell (1994) have defined the North Pacific Index (NPI) as the area-weighted sea level pressure over the region 30°N to 65°N, 160°E to 140°W to measure the decadal variations of atmosphere and ocean in the north Pacific.https://digitalcommons.usu.edu/modern_climatology/1013/thumbnail.jp

Climate Modeling & Downscaling for Semi-Arid Regions

abstract: This study performs numerical modeling for the climate of semi-arid regions by running a high-resolution atmospheric model constrained by large-scale climatic boundary conditions, a practice commonly called climate downscaling. These investigations focus especially on precipitation and temperature, quantities that are critical to life in semi-arid regions. Using the Weather Research and Forecast (WRF) model, a non-hydrostatic geophysical fluid dynamical model with a full suite of physical parameterization, a series of numerical sensitivity experiments are conducted to test how the intensity and spatial/temporal distribution of precipitation change with grid resolution, time step size, the resolution of lower boundary topography and surface characteristics. Two regions, Arizona in U.S. and Aral Sea region in Central Asia, are chosen as the test-beds for the numerical experiments: The former for its complex terrain and the latter for the dramatic man-made changes in its lower boundary conditions (the shrinkage of Aral Sea). Sensitivity tests show that the parameterization schemes for rainfall are not resolution-independent, thus a refinement of resolution is no guarantee of a better result. But, simulations (at all resolutions) do capture the inter-annual variability of rainfall over Arizona. Nevertheless, temperature is simulated more accurately with refinement in resolution. Results show that both seasonal mean rainfall and frequency of extreme rainfall events increase with resolution. For Aral Sea, sensitivity tests indicate that while the shrinkage of Aral Sea has a dramatic impact on the precipitation over the confine of (former) Aral Sea itself, its effect on the precipitation over greater Central Asia is not necessarily greater than the inter-annual variability induced by the lateral boundary conditions in the model and large scale warming in the region. The numerical simulations in the study are cross validated with observations to address the realism of the regional climate model. The findings of this sensitivity study are useful for water resource management in semi-arid regions. Such high spatio-temporal resolution gridded-data can be used as an input for hydrological models for regions such as Arizona with complex terrain and sparse observations. Results from simulations of Aral Sea region are expected to contribute to ecosystems management for Central Asia.Dissertation/ThesisPh.D. Aerospace Engineering 201