WEEKLY CLIMATE NEWS

15-19 October 2018

ITEMS OF INTEREST

An explanation of the term "water year" -- Two weeks ago (on Monday, 1 October 2018) marked the start of water year 2019. The term "water year" or hydrological year has been used nearly a century by hydrologists dealing with surface water supply such as streamflow and other hydrological data. As a matter of convenience, the beginning of this twelve-month period is meant to begin and end during a relatively dry season. In the United States, as well as in other nations in the Northern Hemisphere, the start of the water year on 1 October corresponds to when the season of soil moisture recharge commences as precipitation begins to exceed losses due to evapotranspiration. [AMS Glossary of Meteorology]
NASA's Terra satellite reaches a milestone -- On Saturday, 6 October 2018, NASA's Terra satellite had completed 100,000 orbits around planet Earth after being launched on 18 December 1999. The Terra satellite, which is an orbit approximately 400 miles above the Earth's surface, has five onboard scientific instruments that provide observations of the planet: The Advanced Spaceborne Thermal Emission and Reflection (ASTER) instrument; the Moderate Imaging Spectroradiometer (MODIS); Multi-angle Imaging Spectroradiometer (MISR); Measurements of Pollution in the Troposphere (MOPITT); and the Clouds and Earth's Radiant Energy System (CERES). [NASA Goddard Space Flight Center Feature]
Hurricane Michael was a historic hurricane on several counts -- This past Wednesday, Hurricane Michael made landfall as an unprecedented high-end Category 4 hurricane (on the Saffir-Simpson Scale) along the Florida Panhandle region with a preliminary estimated maximum sustained wind speed of 155 mph at landfall and a minimum air pressure of 919 mb (27.14 inches of mercury).
In terms of central barometric pressure, Michael was the third most powerful hurricane to strike the U.S. mainland, ranked behind the unnamed Labor Day Hurricane of September 1935 (892 mb) and Hurricane Camille (900 mb) in August 1969. However, Michael's central pressure was the lowest on record for any October hurricane to strike the United States.
In terms of maximum sustained wind speed at landfall, Michael was the fourth strongest, behind the Labor Day 1935 hurricane (184 mph), Hurricane Camille (172 mph) and Hurricane Andrew in 1992 (167 mph). Michael is the first Category 4 hurricane on record to make landfall on the Florida Panhandle. [National Weather Service Tallahassee (FL) Office] [Washington Post]
Celebrate Earth Science Week 2018 -- The National Oceanic and Atmospheric Administration, including the National Weather Service, along with NASA, the US Geological Survey and several professional scientific organizations such as the American Geological Institute have recognized this week (14-20 October 2018) as Earth Science Week 2018 to help the public gain a better understanding and appreciation for the earth sciences and to encourage stewardship of the Earth. This year's theme for the 21th annual Earth Science Week is “Earth as Inspiration” that is designed to "emphasize artistic expression as a unique, powerful opportunity for geoscience education and understanding in the 21st century." [American Geological Institute]
Observe Earth Observation Day -- On Tuesday 16 October 2018, Earth Observation Day (EOD) will be observed as a celebration of the NASA/USGS (US Geological Survey) Landsat mission. EOD is a Science, Technology, Engineering, and Mathematics (STEM) educational outreach event sponsored by AmericaView, a nationwide, university-based, and state-implemented consortium, and its partners. The goal of EOD is to engage students and teachers in remote sensing as an exciting and powerful educational tool. Lesson plans and educational resources for educators and students are available from the EOD website. [AmericaView]
Monitoring El Niño and La Niña -- Scientists have suggested that a La Niña event could develop during late meteorological autumn in the Northern Hemisphere and continue into the winter season. This event could affect weather patterns across the United States during the upcoming winter months. For more details on how to monitor these phenomena, please read this week's Supplemental Information...In Greater Depth.

CURRENT CLIMATE STATUS

A dry 2018 water year draws to a close in California -- A meteorologist with NOAA's Climate Prediction Center wrote an "Event Tracker" article for the ClimateWatch Magazine noting many locations across California received precipitation totals that were well below average during the 2018 water year, which ended on 30 September 2018. An animated sequence of monthly maps was generated showing the percent of normal (1918-2010) monthly precipitation across California and surrounding states between October 2017 and September 2018 from data collected by the National Centers for Environmental Information. He noted that this past water year marked a return to the drier than average conditions across California after a relatively wet 2017 water year, which had helped replenish depleted reservoirs. As of the end of last month, the state's two largest reservoirs were below average in terms of capacity because of the dry conditions and the lack of an adequate snow pack from last winter. He wonders if the anticipated El Niño winter ahead will provide California with a wet water year. [NOAA Climate.gov News]

CURRENT CLIMATE MONITORING

Key indicators of global climate change are updated by National Climate Assessment team -- A team of science experts associated with the United States Global Change Research Program (USGCRP) have recently updated a collection of 15 "climate indicators" to show how global climate has been changing. The scientists were using the latest data to produce graphics as part of the process needed to make updates prior to the scheduled release of the new Fourth National Climate Assessment in late 2018. This National Climate Assessment release is in fulfillment of a Congressional mandate to provide updated reports that will serve as an important resource for understanding and communicating climate change science and impacts in the United States. The fifteen indicators show trends that include increases in atmospheric greenhouse gas concentrations, increases in air temperatures, rising sea levels, and decreases in both ice extent and glacier mass. [NOAA Climate.gov News]

CLIMATE FORECASTS

El Niño/Southern Oscillation (ENSO) Diagnostic Discussion & El Niño watch -- NOAA's Climate Prediction Center (CPC) and the International Research Institute for Climate and Society (IRI) recently released their El Niño/Southern Oscillation (ENSO) Diagnostic Discussion showing that while ENSO-neutral conditions were observed to continue through September, the surface waters across the equatorial Pacific Ocean where beginning to warm, as indicated by an increase in the area of above-average sea surface temperatures. (ENSO-neutral conditions indicate neither El Niño or La Niña conditions.) Furthermore, subsurface waters were also warming in the waters of the equatorial Pacific to the east of the Dateline. In addition to oceanic conditions, the state of the tropical atmosphere through September also indicated ENSO conditions, but recent trends would suggest a developing El Niño. Based upon their assessment of the various computer forecast models that they use, the CPC and IRI forecasters have continued a El Niño watch that indicates a 70 to 75 percent chance that El Niño conditions will develop during the remainder of this Northern Hemisphere fall and continue through the boreal winter of 2018-19. Most of the models favor a weak to moderate episode.
An ENSO blog written by a CPC contractor describes the metrics used by CPC and IRI forecasters to identify those oceanic and atmospheric conditions across the tropical Pacific basin in their decision-making process in determining the onset of an El Niño. They believe that the current ENSO-neutral conditions should become a El Niño event during the late fall and early winter 2018-19 (in the Northern Hemisphere), which has led to their continuing a El Niño watch. The blog also has accompanying graphics. [NOAA Climate.gov News]
A detailed and more technical El Niño/Southern Oscillation Diagnostic Discussion with supporting maps and charts is available from CPC.
Forecasters with the Australian Bureau of Meteorology recently issued an updated ENSO forecast from a Southern Hemisphere perspective. They reported that a warming of the tropical Pacific had been detected due to a weakening of the trade winds, which would suggest the onset of El Niño conditions. Furthermore, they felt that with the majority of forecast models indicated a transition to an El Niño. Therefore, they have raised their Bureau's ENSO Outlook to El Niño ALERT, which means that an approximately 70% chance exists for the occurrence of an El Niño in 2018, or roughly triple the normal likelihood. [Australian Government Bureau of Meteorology]

CLIMATE FORCING

Arctic Sea Ice Changes More Slowly with the loss of thick ice -- A scientist at NASA's Jet Propulsion Laboratory recently published an article showing the results based upon a 60-year record of changes in Arctic sea ice thickness from declassified U.S. Navy submarine measurements along with more recent data from four satellites. He found that the sea ice covering the Arctic Ocean has changed since 1958 from predominantly older, thicker ice to mostly younger, thinner ice. He concludes that with so little thick, old ice remaining, the rate of decrease in ice thickness has slowed. New ice grows faster but is more vulnerable to weather and wind, so ice thickness is now more variable, rather than dominated by the effect of warming associated with global climate change. [NASA Jet Propulsion Laboratory Feature]
Key indicators of global climate change are updated by National Climate Assessment team -- A team of science experts associated with the United States Global Change Research Program (USGCRP) have recently updated a collection of 15 "climate indicators" to show how global climate has been changing. The scientists were using the latest data to produce graphics as part of the process needed to make updates prior to the scheduled release of the new Fourth National Climate Assessment in late 2018. This National Climate Assessment release is in fulfillment of a Congressional mandate to provide updated reports that will serve as an important resource for understanding and communicating climate change science and impacts in the United States. The fifteen indicators show trends that include increases in atmospheric greenhouse gas concentrations, increases in air temperatures, rising sea levels, and decreases in both ice extent and glacier mass. [NOAA Climate.gov News]
An international report is meant to be a "wake-up" on a 1.5 Celsius degree warming of Earth -- At the start of last week, the World Meteorological Organization (WMO) released a special report entitled "The Intergovernmental Panel on Climate Change (IPCC) Special Report on Global Warming of 1.5°C." This landmark report is intended to serve as a "wake-up" call about both the huge challenges and the benefits of limiting global warming to 1.5 Celsius degrees above pre-industrial levels in the context of strengthening the global response to the threat of climate change, sustainable development and efforts to eradicate poverty. [WMO Press Release]

PALEOCLIMATE RECONSTRUCTION

Records at tree ring lab used to decode Earth's climate history -- Ed Cook, one of the founding directors of the Columbia University's Lamont-Doherty Earth Observatory Tree-Ring Laboratory, recently was interviewed on his work decoding past climate patterns using tree rings during his 43 years at Lamont. His research involved developing "drought atlases," which are extensive, centuries-long records of wet and dry periods for a given region. These atlases include the North American Drought Atlas in 2004, the Monsoon Asia Drought Atlas in 2010 and the Old World Drought Atlas and Eastern Australia and New Zealand Drought Atlas, both published in 2015. [Lamont-Doherty Earth Observatory News]

CLIMATE AND SOCIETY

Nobel Prize for Economics involves Integrating innovation and climate with economic growth -- The Royal Swedish Academy of Sciences announced last week that it has awarded the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel 2018 to William D. Nordhaus of Yale University "for integrating climate change into long-run macroeconomic analysis" and Paul M. Romer of New York University's Stern School of Business "for integrating technological innovations into long-run macroeconomic analysis." [Nobel Prize Organization Press Release]
Earthweek -- Diary of the Planet [earthweek.com]

Concept of the Week: Seawater Salinity and Carbon Dioxide

The contemporary concern regarding global climate change has caused scientists to study the various factors that govern the ocean's ability to absorb atmospheric carbon dioxide. Concentrations of atmospheric carbon dioxide, a greenhouse gas, are on the rise primarily because of increased burning of fossil fuels. Higher levels of atmospheric carbon dioxide may be contributing to increased global temperatures, a condition often identified as global warming. The ocean's role in regulating the concentration of atmospheric carbon dioxide depends on the temperature, salinity, and biological components of surface waters.

Studies show that the ocean's ability to absorb carbon dioxide is primarily temperature dependent. As noted in Chapter 8 of your textbook, gases are more soluble in cold seawater than warm seawater. Hence, changes in sea surface temperature affect the ability of the ocean to absorb carbon dioxide. We also found in Chapter 1, photosynthetic organisms assimilate carbon dioxide and release oxygen. Through cellular respiration, all organisms release carbon dioxide. Therefore, biological activity affects the ocean's ability to absorption of atmospheric carbon dioxide.

What about the effects of changes in salinity on the ocean's uptake of atmospheric carbon dioxide? Research from the Pacific Ocean near Hawaii provides some insight on this question. For nearly 20 years, scientists have been collecting physical, chemical and biological data through a large column of ocean water at Station ALOHA, a sampling site about 100 km (62 mi) north of Oahu that appears representative of oceanic conditions in the central North Pacific. In 2003, David M. Karl, a biogeochemist at the University of Hawaii in Honolulu, reported a decline in the rate at which surface ocean waters were absorbing carbon dioxide from the atmosphere. In 2001, the rate of carbon dioxide uptake was only about 15% of the rate in 1989. Why the change in carbon dioxide uptake? In this region of the Pacific north of Hawaii, sea surface temperatures showed no significant change during the period of observation, but precipitation decreased and evaporation increased. Less precipitation associated with drought coupled with higher rates of evaporation caused the surface water salinity at ALOHA to increase by about 1%. Increasing salinity inhibits water's ability to absorb gases including carbon dioxide. Karl and his colleagues attribute 40% of the decline in the ocean's carbon dioxide uptake to the saltier waters. The balance of the decline may be due to changes in biological productivity or ocean mixing.

Projected changes in global climate indicate significant changes in precipitation around the globe including reduced precipitation over various large areas of the oceans, resulting in potential "drought" conditions. Since changes in oceanic salinity result from changes in precipitation, the contribution that salinity plays on future assimilation of atmospheric carbon dioxide by the ocean also becomes an important consideration.

Historical Events:

15-17 October 2005...The summit of Mount Washington, NH, the highest peak in the Northeast received 34 inches of snow between Saturday and Monday. The 24-hour record for the most snowfall was broken when 25.5 inches of snow piles up between noon Sunday and noon Monday. (The Weather Doctor)
16 October 1913...The temperature in Downtown San Francisco soared to 101 degrees to equal their record for October. (The Weather Channel)
16 October 1988...The afternoon high temperature of 100 degrees at Red Bluff, CA was the latest such reading of record for so late in the autumn season. (The National Weather Summary) (Storm Data)
17-18 October 2005...Heavy rain fell on Las Vegas, NV over the two-day period, with a rainfall total of 1.42 inches, which broke the full month record for October set in 1992. (The Weather Doctor)
17-19 October 2007...According to NOAA's Storm Prediction Center, 87 tornadoes were reported in the United States on these three days -- a new record outbreak for the month. With the outbreak, the monthly total of confirmed tornado reached 105, the second highest for October, behind the 117 in October 2001 since records began in 1950. Over 300 reports of severe weather were filed on 18 October across the lower and mid-Mississippi Valleys. (The Weather Doctor)
18 October 1984...Heavy snow began falling late on the 17^th at Salt Lake City and when it ended, 18.4 inches fell, setting a new 24-hour snowfall record. (Intellicast)
18-19 October 2005...Hurricane Wilma developed a tiny, well-defined eye and began intensifying rapidly, reaching Category 5 strength with a record-setting pressure of 882 millibars (26.04 inches of mercury) by 19 October. The rapid intensification from tropical storm to Category 5 hurricane in 24 hours was the fastest ever recorded in the Atlantic Ocean, and the second-fastest worldwide, after Super Typhoon Forrest. (National Weather Service files)
20 October 2004...Rain at two stations in Nevada broke the state's previous 24-hour maximum precipitation record of 7.13 inches set previously at Mt. Rose Highway Station (31 January 1963). The new state record of 9.78 inches was established at Mt. Charleston, while Kyle Canyon also broke the old record with 8.75 inches. (Accord Weather Guide Calendar)
21 October 1996...Portland, ME received 13.32 inches of rain to set a 24-hour maximum precipitation record for the Pine Tree State. (NCDC)

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