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Researchers from the Cooperative Institute of Mesoscale Meteorological Studies (CIMMS) and the National Severe Storms Laboratory (NSSL) recently published a study in the international “Advances in Meteorology” journal highlighting important advances toward making storm-scale forecasts of supercells.  Researchers conducted two storm-scale experiments using model jumping off points from either a fixed physics (same sets of physics schemes) or a multiple physics (different combinations of physics schemes) mesoscale ensemble system to see which method better predicts a tornadic supercell storm. Their results show that the ensemble with jumping off points from the multiple physics ensemble forecast provides more realistic forecasts of the significant tornado parameter, dry line structure, and near surface variables. The probabilities of strong low-level updraft helicity from the multiple physics ensemble forecast correlate better with observed tornado and rotation tracks than probabilities from fixed physics ensemble forecast. 

Background: Researchers from the Cooperative Institute of Mesoscale Meteorological Studies (CIMMS) and the National Severe Storms Laboratory (NSSL) recently published “The Impact of Mesoscale Environmental Uncertainty on the Prediction of a Tornadic Supercell Storm Using Ensemble Data Assimilation Approach” in the international Advances in Meteorology journal. To view article, click here.. 

Significance: This work suggests that incorporating physics diversity across the ensemble can be important to successful probabilistic storm-scale forecast of supercell thunderstorms, which is the main goal of NOAA’s Warn-on-Forecast initiative.

The journal, Atmospheric Chemistry and Physics, just published results of a recent experiment examining two stratosphere-to-troposphere (STT) events observed over California. NOAA/NESDIS researchers at the Cooperative Institute for Meteorological Satellite Studies (CIMSS), University of Wisconsin-Madison, are collaborating with NASA scientists, university researchers and air quality and public health scientists to analyze airborne and in situ measurements of ozone and other trace gases that accompany STT events. STT events are of concern because the ozone may increase to dangerous levels, triggering public health warnings.

Scientists at the Cooperative Institute for Marine Resources Studies (CIMRS) are investigating sounds generated by icebergs in the Southern Ocean and their potential to affect marine animals and ecosystems.  While the steady increase in global shipping traffic has been identified as a primary cause of rising ocean noise level, the disintegration of large icebergs was found to be another significant noise source that influences the soundscape of the southern hemisphere. 

Background

Two icebergs, B15a and C19a, collectively larger than Connecticut, calved off the Ross Ice Shelf in early 2000s and drifted eastward to the warmer South Pacific Ocean in late 2007.  For the next 1.5 years, while these icebergs were rapidly melting, they affected water circulation and marine ecosystem in their vicinity. 

From 2008 to early 2009, the disintegration of B15a and C19a continuously projected loud low frequency sounds into the water column. The sounds propagated efficiently to lower latitudes, thus influencing the soundscape of the entire South Pacific basin.  The icebergs’ sounds were recorded at Juan Fernandez Island (34^oS, 79^oW) by hydrophones maintained by Comprehensive Nuclear-Test-Ban Treaty Organization.  The sounds also propagated across the equator (~10,000 km) and were recorded at 8^oN, 110^oW by a hydrophone maintained by NOAA Pacific Marine Environmental Laboratory (PMEL) and CIMRS.  The noise level was ~7 dB and ~3 dB higher than baseline years, respectively.  The icebergs’ sounds dominated frequency ranges below 100 Hz in which marine mammals, such as baleen whales, vocalize for communication, navigation and forage behaviors.  

Significance

Some large icebergs have lifespans over a decade.  This study shows that icebergs the size of B15a and C19a can generate a considerable amount of sound energy, which can propagate across ocean basins, influencing the ocean acoustic environment and potentially marine mammals’ acoustic behaviors for the duration of the iceberg’s disintegration.    

The study meets NOAA PMEL’s goals of (a) to acquire long-term data sets of the global ocean acoustics environment and (b) to identify and assess acoustic impacts from human activities and natural processes on the marine environment. 

Contact: Haru Matsumoto, Oregon State University CIMRS Assistant Professor, Research, matsumoh@onid.oregonstate.edu

CIMEC investigator Marc Mangel is lead author on “A perspective on steepness, reference points, and stock assessment,” published in The Canadian Journal of Fisheries and Aquatic Sciences[1]. This publication is a milestone in work funded by PIFSC and FED/SWFISC and has profound implications for the interpretation of stock assessments.

Background:  One of the major objectives of stock assessments is the determination of Reference Points (RPs) that are frequently used to help guide policy.  Common RPs include: unfished biomass B₀; the biomass leading Maximum Sustainable Yield (MSY) B_MSY ; the rate of fishing mortality that gives MSY, F_MSY; and the ratio of Spawning Biomass Per Recruit when the population is fished at B_MSY to the Spawning Biomass Per Recruit of an unfished population SPR_MSY.

It has become common in the last 20 years to discuss the resilience of a population to fishing using a parameter named steepness, which is defined as the fraction of recruitment from an unfished population when the spawning stock biomass declines to 20% of its unfished level. Fixing both steepness and adult natural mortality rate is common in stock assessments. Mangel and his collaborators have shown that in such cases, with either of the commonly used stock recruitment relationships, many important RPs are then fixed before any analysis is done.

Significance:  This work has implications for how stock assessments are conducted and interpreted, particularly as assessments are being attempted on stocks with progressively more limited data.

One option is not to fix steepness and the natural mortality but to estimate them from the data. Here, thorough simulation analyses can be used to determine what kinds of data would be necessary so that steepness and natural mortality could be estimated as part of a stock assessment.  Utilized by Brodziak and Mangel, this approach is facilitated by developing prior distributions for steepness using reproductive ecology.

Alternatively, one may seek a SRR for which RPs are not fixed when steepness and life history parameters are fixed. Work in this direction is in progress by Dick and MacCall and its feasibility has already been demonstrated in a stock assessment of cowcod, done in conjunction with CSTAR graduate student researcher Maria DeYoreo.

An alternative interpretation of these findings is that management policy with biomass targets or rebuilding plans on a fixed time table with specified probability is often overstepping what can realistically be expected from a defensible assessment of an individual stock. 

Point of contact: Marc Mangel (msmangel@ucsc.edu)

 [1] (CJFAS, Volume 70,pgs 930-940 (2013). Co-authors are Jon Brodziak, EJ Dick, Alec MacCall, and Steve Ralston (Fisheries Ecology Division, Southwest Fisheries Science Center, FED/SWFSC), Robyn Forrest (Fisheries and Oceans Canada, Nanamio, BC), and CSTAR undergraduate research fellow Roxanna Pourzand.

Using satellite data, shipboard plankton surveys and in situ data, U.S. and Spanish scientists have provided the first quantitative comparison of the environmental characteristics of the only two known spawning habitats of Atlantic bluefin tuna (Thunnus thynnus). Collaborators included academic (the Cooperative Institute for Marine and Atmospheric Studies and Oregon State University), government (National Marine Fisheries Service and the Spanish Institute for Oceanography) and private industry (Roffers Ocean Fishing Forecasting) scientists.  Results from their collaborative study were published in Marine Ecology Progress Series.  

Background: Bluefin tuna in the north Atlantic are divided into two stocks: a western stock, which spawns in the Gulf of Mexico, and an eastern stock, which spawns in the Mediterranean Sea. Using larval catches from plankton surveys, and environmental variables from in situ measurements and remotely sensed satellite data, the characteristics of the two spawning habitats were compared.   Results highlighted the importance of warm (23-28°C), low chlorophyll areas with moderate current velocities.  Bluefin tuna spawning in the Gulf of Mexico do so in offshore waters just outside of the Loop Current, while in the western Mediterranean, they spawn at a confluence of inflowing Atlantic waters and saltier resident Mediterranean surface water. 

Significance: Atlantic bluefin tuna stocks are at historically low levels, and both eastern and western stocks are currently managed under stock rebuilding plans.  Simply limiting catch may not be sufficient for stocks to recover. A quantitative assessment of the characteristics of the natural spawning habitats is essential to understand the actual constraints upon larval growth, larval survival, and ultimately recruitment into the fishery. This research project was undertaken and funded in support of the National Oceanic and Atmospheric Administration mission goal to sustain marine fisheries and fisheries habitats within healthy oceans.

Contact Information: Barbara Muhling, bmuhling@rsmas.miami.edu