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Hi All, December was relatively warm and wet for West Tennessee, while areas further east were closer to average. The main weather and climate stories of December 2024 included the strong blast of cold air early in the month that led to widespread light snowfall and record cold temperatures from December 3-6, and two cold fronts that brought strong thunderstorms, localized flash flooding, some small hail, and strong winds to the state on December 18 and December 28-29. Heavy rains on the 29th led to flash flooding and closure of roads and temporary bridges in parts of Carter County that were impacted by severe flooding in September from Helene. December was a busy month in the climate office and we didn't get our November summary out to you, so that is also attached here. You can view all previous summaries in the Monthly Reports section of our website as well. With 2025 well underway, we will also be releasing our 2024 Annual Climate Summary within the next few days so be on the lookout for that. We hope everyone is staying warm! Andrew & Wil Tennessee Climate Office East Tennessee State University Department of Geosciences 310 Ross Hall Johnson City, TN 37614

This study examines the spatial and temporal characteristics of the surface air temperature in Portland, Oregon. Spatial temperature patterns indicate that the dominant control factors on seasonal temperature distribution are local topography, elevation, and urban-rural differences in surface structure. A heat island exists in the Portland area; the intensity of the heat island rang€s from 4° to 10° F, and varies throughout the year. The strongest heat island is found in the July minimum temperature. Temperature distribution in Portland and the adjacent area is affected by winds and rainy conditions, but less influenced under overcast skies. The long-term temperature over the last century shows that Portland's mean annual temperature trends are 0.057° F/yr and 0.052° F/yr in the two warming periods 1900-1940 and 1961-1984, respectively, and these warming trends are largely due to warming in spring and early summer as well as in winter months except January. Comparisons between Portland and other local non-urban climatic stations show a general warming trend in Portland since the end of the last century, which is 0.028° F/yr in the mean annual temperature, and 0.017° F/yr in maximum temperature after the regional trends are removed. Monthly mean temperature in July and January demonstrate a warming by 0.023° F/yr and 0.015° F/yr at Portland, respectively. All these warming trends are due mainly to the impact of urbanization. It is found that the cooling effect on the northern Willamette Valley due to the presence of the Columbia Gorge is most noticeable in the daytime and in January.

Local climate action plans have become more prevalent in recent years yet information on their success is limited. While unlikely, on their own, to be able to mitigate enough carbon emissions to prevent catastrophic impacts of global temperature increase, local climate planning has the potential to play an important role in a number of key ways. Cities have traditionally exercised control in areas that have GHG abatement potential at low cost (e.g. building codes, land use, energy procurement) and the total population represented by cities committed to GHG reduction efforts is not insignificant and continues to grow. The extent to which local climate plans can serve as a meaningful element in a larger (but currently woefully inadequate) policy picture, will depend on their ability to set aggressive goals, dedicate resources, test innovative strategies, and measure progress systematically. Looking at the plans and progress reports of five U.S. cities, many have set aggressive goals and created innovative programs that could be replicated at other levels of government, but most are somewhat lacking in measuring and reporting progress metrics and financial resources committed to these efforts. For local climate planning to contribute significantly to broader climate policy, it will need to develop more rigorous progress metrics so the highest yield, lowest cost abatement strategies can be identified and advanced in other cities and at higher levels of government. / text

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

The climate of the eastern section of the Sahelian latitude, especially over the Eritrean subdomain, is often associated with long drought episodes from which the atmospheric mechanisms are poorly understood. In an effort to improve our knowledge of weather and climate systems over this region, the PRECIS Regional Climate Model (RCM) from the United Kingdom (UK) was obtained and implemented. Such a climate model that is based upon the physical laws of nature has the ability to simulate regional-scale atmospheric patterns, and therefore, may significantly contribute to our understanding of local atmospheric processes. In this dissertation the assessment of past regional climate trends from both observations and model simulations, and the simulation of scenarios for possible future climate change were regarded as important. To investigate this, the PRECIS RCM was first nested over the Eritrean domain into the “atmosphere only” HadAM3H global General Circulation Model (GCM) and forced at its lateral boundaries by a 30-year present-day (1961-1990) integration of the same global model. Secondly, the PRECIS RCM was constrained at its lateral boundary by the “fully coupled” HadCM3 GCM (for Sea Surface Temperatures (SSTs) and sea-ice) and its improved atmospheric component (HadAM3H GCM). The latter simulations provided boundary conditions for the A2 and B2 future emission scenarios (Special Report on Emission Scenarios (SRES)) to simulate a 20-year (2070-2090) projection of future climate. These experiments allowed for verification of both spatial and temporal present-day climate simulations, as well as possible future climate trends as simulated by the PRECIS RCM over the Eritrean domain, with specific emphasis on temperature and moisture related variables. The study indicates that PRECIS RCM climate simulations are mostly in harmony with observed spatial patterns. This skill may be attributed to the full representation of the climatic system (land surface, sea, ice, atmosphere and atmospheric chemistry such as sulphur and greenhouse gasses) in the model configuration. However, when comparing PRECIS RCM results with the much coarser resolution (2.5ox2.5o) National Centre for Environmental Prediction (NCEP) reanalysis data, obvious differences do occur. These differences are not necessarily the result of poor model performance, but may be attributed to more detailed simulations over the finer RCM grid (0.44o x 0.44o). Future climate scenario simulation with the PRECIS RCM over Eritrea produce increased surface temperature in both the A2 and B2 SRES scenario integrations, relative to the present climatology. This temperature increase also appears in the driving GCM (HadCM3) as well as in other GCM results from the Inter Governmental Panel for Climate Change (IPCC) initiative. There are, however, mixed signals in rainfall projections. According to PRECIS RCM results, rainfall is expected to increase in most of the Eritrean region. Copyright 2005, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Beraki, A F 2005, Climate change scenario simulations over Eritrea by using a fine resolution limited area climate model : temperature and moisture sensitivity , MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02102006-152327 / > / Dissertation (MSc)--University of Pretoria, 2007. / Geography, Geoinformatics and Meteorology / Unrestricted