CW3E Publication Notice: Response of Sea Surface Temperature to Atmospheric Rivers

CW3E Publication Notice

Response of Sea Surface Temperature to Atmospheric Rivers

June 18, 2024

A new article titled “Response of sea surface temperature to atmospheric rivers” by Tien-Yiao Hsu (SIO /CW3E), Matthew R. Mazloff (SIO), Sarah T. Gille (SIO), Mara A. Freilich (Brown University), Rui Sun (SIO/CW3E) and Bruce D. Cornuelle (SIO) was published in Nature Communications on June 12, 2024. This work investigates the impact of atmospheric rivers (ARs) on sea surface temperature (SST) over the North Pacific by analyzing 25 years of ocean reanalysis data using an SST budget equation. Authors show that in the region of strong ocean modification, ocean dynamics can offset over 100% of the anomalous SST warming that would otherwise arise from atmospheric forcing (Figure 1). Among all ocean processes, ageostrophic advection and vertical mixing (diffusion and entrainment) are the most important factors in modifying the SST tendency response. The SST tendency response to ARs varies spatially. For example, in coastal California, the driver of enhanced SST warming is the reduction in ageostrophic advection due to anomalous southerly winds. Moreover, there is a large region where the SST shows a warming response to ARs due to the overall reduction in the total clouds and subsequent increase in total incoming shortwave radiation. This work adds tangible understanding to the Subseasonal to Seasonal Prediction of Extreme Weather priority area in CW3E’s Strategic Plan, where SST prediction is a crucial boundary condition.

Figure 1. (Figure 5 from Hsu et al. 2024). The response of sea surface temperature (SST) tendency to atmospheric rivers (ARs), decomposed into distinct contributing processes. Variables shown are: (a) Θ̅̇loc, (b) Θ̅̇ocn, (c) Θ̅̇adv, (d) Θ̅̇mix, (e) Θ̅̇det, (f) Θ̅̇sfc, (g) Θ̅̇sw, (h) Θ̅̇lw, (i) Θ̅̇sen, and (j) Θ̅̇lat. Each panel shows the mean of the composite anomalous SST tendency associated with a particular process (shading) and its standard deviation (contours). Dotted areas show response regions that pass the significance test (p = 0.05). For each grid point, we compute the mean and standard deviation by grouping all of the AR day data. The significance test is tested against the climatology group, i.e., every single day. The anomalous SST tendencies Θ̅̇dilu and Θ̅̇hdiff are very small such that they are not shown.

Hsu, T.-Y., Mazloff, M. R., Gille, S. T., Freilich, M. A., Sun, R., & Cornuelle, B. D. (2024). Response of sea surface temperature to atmospheric rivers. Nature Communications, 15, 508. https://doi.org/10.1038/s41467-024-48486-9

AR Recon Program Endorsement by World Meteorological Organization

AR Recon Program Endorsement by World Meteorological Organization

April 26, 2024

Atmospheric River Reconnaissance (AR Recon), a CW3E-led program in partnership with the National Centers for Environmental Prediction and the U.S. Air Force, was recently endorsed by the World Meteorological Organization (WMO) as a World Weather Research Programme (WWRP) endorsed project.

The WMO WWRP promotes research to improve weather prediction and its impacts on society. The improvements in science and operational predictions are driven by international cooperation, and intended to drive sustainable development. As one of 10 WWRP endorsed projects, this represents a strong show of support for a key mission and a major programmatic milestone for AR Recon, which works to support improved prediction of landfalling atmospheric rivers on the U.S. West Coast.

Consistent with WWRP’s key objectives, AR Recon has developed the tools and network necessary to incrementally improve the warning process for extreme weather events, and reduce prediction uncertainty. Key sponsors have been the U.S. Army Corps of Engineers and the California Department of Water Resources, who are working with CW3E and other partners to advance their goals of using improved AR prediction to inform water and infrastructure management (e.g., for Forecast Informed Reservoir Operations – FIRO).

Since program inception, AR Recon observational campaigns have been conducted in collaboration with international experts from organizations including CW3E, Scripps Institution of Oceanograpy, the National Oceanic and Atmospheric Administration, the Naval Research Laboratory, the National Weather Service, the National Center for Atmospheric Research, the European Centre for Medium-Range Weather Forecasts, the U.S. Air Force, and other academic institutions. The operations to support these observational campaigns, which now run from November 1st through March 31st, continue to increase in pace and intensity as capability is added and the geographic area of interest expands globally.

We would like to express our appreciation to the WMO for selecting AR Recon for the WWRP. We look forward to engaging further with the WMO and international partners to support WWRP objectives through AR Recon.

For more detailed information about the AR Recon program, please see the AR Recon webpage.

Summary of CW3E Outlooks During Water Year 2024

Summary of CW3E Outlooks During Water Year 2024

April 22, 2024

CW3E summarizes and disseminates key forecast information about potentially hazardous weather over the Western US, with a strong emphasis on landfalling ARs, as part of the California Atmospheric River (AR) and Forecast Informed Reservoir Operations (FIRO) programs. These activities consist of written outlooks, “quick looks”, and post-event summaries of high-impact storms. The outlooks and quick looks provide valuable information and situational awareness guidance to stakeholders, such as the California Department of Water Resources and local water agencies, as well as the general public.

CW3E created and posted a total of 25 outlooks, 27 quick looks/Twitter threads, and 10 event summaries during October 2023 through March 2024. During a particularly active four-week period between 21 January 2024 and 17 February 2024, CW3E posted six outlooks and five quick looks. This period included the record-breaking precipitation and severe flooding event in San Diego County on 22 January 2024 and a strong AR in early February 2024 that produced >10 inches of rain in the Los Angeles metro area. Some locations in Southern California received more than a year’s worth of precipitation in the first 3 weeks of February 2024.

The CW3E outlooks and post-event summaries focus on storm events over the Western US; however, the team also prepared outlooks and event summaries for two exceptionally strong ARs that produced extreme precipitation and widespread flooding over the Eastern US in mid-December 2023 and early January 2024. These activities were sponsored by the nationwide expansion efforts of the FIRO program and funded projects with the NOAA Cooperative Institute for Research to Operations in Hydrology (CIROH).

A more recent initiative supported by the AR Program has involved the creation and posting of subseasonal-to-seasonal (S2S) forecast information via regularly scheduled Subseasonal and Seasonal Outlooks. While the AR outlooks and quick looks focus on weather time scales (forecast lead times of up to 10 days), the Subseasonal and Seasonal Outlooks focus on 2–6 week and 1–3 month lead times, respectively, and are posted between November and March. These longer time scales are a primary concern for the water resource management community, especially given the implications of cool-season precipitation and snowpack for drought and water supply in the Western US. CW3E posted its first S2S outlook in December 2021, and the S2S outlooks team has continuously worked to augment and improve the content in these updates based on an iterative process with direct input provided by practitioners.

In Water Year (WY) 2024, CW3E began posting subseasonal and seasonal forecast information in two unique outlooks; the Subseasonal Outlooks are typically posted weekly, and the Seasonal Outlooks are posted monthly. Both the Subseasonal and Seasonal Outlooks include information from experimental forecast products developed at CW3E and collaborating institutions such as NOAA and the International Research Institute for Climate and Society (IRI), as well as a single prediction based on a synthesis of the products. During WY 2024, CW3E posted 17 Subseasonal Outlooks and 5 Seasonal Outlooks. CW3E will solicit further feedback from users this year and aims to incorporate additional forecast products currently under review into its WY 2025 Subseasonal and Seasonal Outlooks.

Category

Oct

Nov

Dec

Jan

Feb

Mar

Total

AR/Precipitation Outlooks

4

2

5

9

5

0

25

Quick Looks/Twitter Threads

3

4

7

4

3

6

27

Event Summaries

0

0

3

3

3

1

10

Subseasonal Outlooks

0

2

3

5

3

4

17

Seasonal Outlooks

0

1

1

1

1

1

5

CW3E Publication Notice: Local and Object-based Perspectives on Atmospheric Rivers Making Landfall on the Western North American Coastline

CW3E Publication Notice

Local and Object-based Perspectives on Atmospheric Rivers Making Landfall on the Western North American Coastline

April 10, 2024

A new article titled, “Local and Object-based Perspectives on Atmospheric Rivers Making Landfall on the Western North American Coastline” was recently published in the American Meteorological Society’s Journal of Hydrometeorology by Wen-Shu Lin (CW3E), Joel Norris (CW3E), Michael DeFlorio (CW3E), and Marty Ralph (CW3E). This work contributes to the Atmospheric River Research and Applications priority area in CW3E’s 2019-2024 Strategic Plan by investigating characteristics of atmospheric rivers (ARs) affecting the western North American coastline, and was sponsored by the California Department of Water Resources Atmospheric River Program and the US Army Corp of Engineers.

This paper presents the climatology and variability of landfalling ARs over the western North American coastline, including AR intensity, duration, coastal extent, IVT temporal evolution, and synoptic conditions. ARs are defined by the Ralph et al. (2019) and Guan and Waliser (2019) AR detection algorithms for the local and object-based perspectives, respectively. The intensity of ARs is ranked following the classification scheme of Ralph et al. (2019). The local perspective shows higher AR frequency in Oregon and Washington and lower AR frequency in Southern California and southeastern Alaska, regardless of AR ranks (Fig. 1 left). Strong ARs are less frequent but with a greater seasonal cycle than weak ARs. However, the object-based perspective shows less geographical variation of AR frequency (Fig. 1 right). Although there is nearly no seasonal cycle of AR frequency in Alaska, ARs intensify in summer but weaken in winter.

Our results using object-based analysis additionally highlight that the strong ARs at lower latitudes are associated with stronger wind than weak ARs, while strong ARs at higher latitudes are associated with greater moisture than weak ARs (Fig. 2b,c). IVT at the AR core is largest for stronger ARs in Oregon and Washington and decreases poleward and equatorward (Fig. 2a). One common feature for ARs in object-based analysis is that both IVT in the AR core and cumulative IVT along the coastline usually increase from the first to second day for strong ARs but decrease after the first day of landfall for weak ARs, and hence the strength of an AR could not solely be determined by the IVT magnitudes upon ARs making landfall. These results are important to more comprehensively understand the relationship between AR characteristics and the resulting impacts on communities and the landscape.

Figure 1. Adapted from Figs. 2 and 5 from Lin et al. (2024). Left: The R19 AR frequency for (a) annual mean [hours month-1], (b) NDJFM departure from the annual mean [hours month-1], and (c) JJASO departure from the annual mean [hours month-1] for 250-km intervals along the western North American coastline. Right: AR frequency associated with the GW19 AR objects for (a) annual mean [hours month-1], (b) NDJFM departure from the annual mean [hours month-1], and (c) JJASO departure from the annual mean [hours month-1] for 250-km intervals along the western North American coastline.

Figure 2. Fig. 9 from Lin et al. (2024). (a) IVT [kg m-1 s-1] at the core location, (b) average IWV [kg m-2] at core location, (c) average ratio of IVT to IWV [m s-1] at core location, and (d) cumulative IVT [1014 kg] along the coastline and over the duration of the AR averaged over the GW19 AR objects in six coastal regions.

Lin, W., Norris, J. R., DeFlorio, M. J., & Ralph, F. M. (2024). Local and Object-based Perspectives on Atmospheric Rivers Making Landfall on the Western North American Coastline. Journal of Hydrometeorology (published online ahead of print 2024). https://doi.org/10.1175/JHM-D-22-0155.1

CW3E Subseasonal Outlook: 8 March 2024

CW3E Subseasonal Outlook: 8 March 2024

March 8, 2024

Click here for a pdf of this information.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Summary provided by J. Wang, C. Castellano, Z. Yang, M. DeFlorio, and J. Kalansky; 8 March 2024

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*Outlook products are considered experimental

CW3E Event Summary: 28 February – 3 March 2024

CW3E Event Summary: 28 February – 3 March 2024

8 March 2024

Click here for a pdf of this information.

Atmospheric River and Winter Storm Produce Heavy Snow Across Western US

  • An atmospheric river (AR) and a slow-moving mid-level trough fueled a long-duration precipitation event over the Western US during 28 Feb – 3 Mar.

The AR:

  • The AR made landfall over the Pacific Northwest late on 27 Feb, producing AR2 conditions (based on the Ralph et al. 2019 AR Scale) along the coast of southern Washington, Oregon, and far Northern California.
  • After the initial landfalling AR weakened, a second pulse of moisture transport brought another period of AR conditions to Northern and Central California.
  • The initial AR landfall and the second pulse of moisture transport combined to produce AR1–2 conditions in the foothills of the Sierra Nevada and played a key role in supporting very heavy snowfall accumulations.

Impacts:

  • The heaviest precipitation (> 6 inches liquid equivalent) was observed in the Pacific Coast Ranges and Sierra Nevada.
  • An estimated 4–10 feet of snow fell in the Northern and Central Sierra Nevada, with the highest totals near Lake Tahoe.
  • About 2–4 feet of snow fell in the Olympic Mountains, Cascades, Klamath Mountains, and Southern Sierra Nevada.
  • Low freezing levels also facilitated significant snowfall accumulations (> 12 inches) in the Willapa Hills, Oregon Coast Ranges, and Northern California Coast Ranges.
  • This event provided a substantial boost to seasonal snowpack in the Sierra Nevada, with many stations reporting snow water equivalent (SWE) increases of 8–12 inches (~20–30% of the typical peak SWE) over a 5-day period.
  • Heavy snowfall and high winds created extremely dangerous travel conditions, resulting in closures of I-80 and US-395.

Click images to see loops of GFS 500-hPa Geopotential Height/Vorticity and IVT analyses

Valid: 1200 UTC 27 February – 1200 UTC 4 March 2024

GOES West GEOCOLOR Composite: NOAA/NESDIS/STAR
Valid: 0000 UTC 28 February – 0000 UTC 2 March 2024


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Summary provided by C. Castellano, S. Bartlett, P. Iniguez, J. Kalansky, and G. Lewis; 8 Mar 2024

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CW3E Subseasonal Outlook: 1 March 2024

CW3E Subseasonal Outlook: 1 March 2024

March 1, 2024

Click here for a pdf of this information.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Summary provided by Z. Yang, C. Castellano, J. Wang, M. DeFlorio, and J. Kalansky; 1 March 2024

To sign up for email alerts when CW3E post new AR updates click here.

*Outlook products are considered experimental

CW3E Event Summary: 18-20 February 2024

CW3E Event Summary: 18-20 February 2024

27 February 2024

Click here for a pdf of this information.

Low-Pressure System and Atmospheric River Produce Heavy Rain and Snow in CA

  • An atmospheric river (AR) associated with a slow-moving area of low pressure brought widespread precipitation to California during 18–20 Feb.

The AR:

  • A deepening mid-level trough off the US West Coast interacted with a remnant plume of subtropical moisture, leading to an AR landfall over California on 18 Feb.
  • AR1–2 conditions (based on the Ralph et al. 2019 AR Scale) were observed in coastal Northern and Central California.
  • As the eastward progression of the trough stalled and the synoptic-scale flow became more southerly, the AR briefly re-intensified over Southern California, prolonging precipitation over the Transverse Ranges.

Impacts:

  • The heaviest precipitation occurred in the western Transverse Ranges, with more than 10 inches in some locations.
  • At least 1–3 feet of snow fell in the Sierra Nevada, with higher amounts in the vicinity of Lassen Peak.
  • Heavy rain falling on moist soils caused minor riverine flooding in the Sacramento Valley.
  • Flooding and mudslides closed portions of US-101, SR-1, SR-33, and SR-150 in Ventura and Los Angeles Counties.
  • Portions of coastal Southern California have received more than 75% of their normal total annual precipitation during the first 3 weeks of February.
  • Unusually cool and wet conditions during the month of February have facilitated a dramatic improvement in snowpack conditions throughout the state.

Click images to see loops of West-WRF IVT/IWV analyses and forecasts

Valid: 0000 UTC 18 February – 0000 UTC 21 February 2024


 

 

 

 

 

 

 

 

 

 

 

Summary provided by C. Castellano, S. Bartlett, P. Iniguez, and S. Roj; 27 Feb 2024

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CW3E Publication Notice: Vientos – A new satellite mission concept for 3D wind measurements by combining passive water vapor sounders with Doppler wind lidar

CW3E Publication Notice

Vientos – A new satellite mission concept for 3D wind measurements by combining passive water vapor sounders with Doppler wind lidar

February 19, 2024

In the recent publication “Vientos – A new satellite mission concept for 3D wind measurements by combining passive water vapor sounders with Doppler wind lidar” in the Bulletin of the American Meteorological Society by CW3E collaborator and University of Arizona professor Xubin Zeng, among co-authors across institutions including CW3E’s Anna Wilson, propose a new satellite mission to address the challenge in accurately characterizing three-dimensional distribution of horizontal wind vectors (3D winds): Vientos. This proposed satellite mission will combine 2 or more passive water vapor sounders with Doppler wind lidar to accurately measure these 3D winds. This work contributes to CW3E’s 2019-2024 Strategic Plan, in particular the Priority Area dedicated to Atmospheric River Research and Applications by suggesting a transformative modernization of atmospheric measurements.

3D winds are integral to the Earth system, and yet, we do not currently have a method of accurately observing 3D winds with requisite space/time coverage. Information on 3D wind structures in and around atmospheric rivers in particular has the potential to be transformational for our understanding of the underlying processes. Further, our reliance on reanalysis data has been proved by recent studies to contain some systematic dynamical biases and errors. Thus, the need for Vientos is clear. The feasibility of the Vientos concept, which would retrieve 3D atmospheric motion vectors through tracking the movement of water vapor, followed by a bias correction using lidar measurements, has been proved doable by recent missions that explore combining active and passive observations as part of the global observing system.

The Vientos mission would be able to address many scientific questions and contribute to a variety of applications. In addition to 3D wind observations, it would also provide 3D water vapor and temperature data while wind lidar provides aerosol measurements of the near storm environment (Figure 1, from the paper). This could provide many benefits to areas including but not limited to: numerical weather predictions, flight route planning in aviation, Forecast Informed Reservoir Operations (FIRO), wind energy, tracking transport of pollutants and aerosols, climate model evaluations, and carbon monitoring for international negotiations and policy making. Lastly, the essay explores different possible architectures of the project, each providing different resolutions and coverage based on budgets available coinciding with currently planned satellite missions.

Vientos emphasizes the synergy between passive sounders and wind lidar in a way that could fill a critical gap in Earth system scientific knowledge. To read more about the Vientos concept, access the entire publication here.

Zeng, X., Su, H., Hristova-Veleva, S., Posselt, D. J., Atlas, R., Brown, S. T., Dixon, R. D., Fetzer, E., Galarneau, T. J., Jr., Hardesty, M., Jiang, J. H., Kangaslahti, P. P., Ouyed, A., Pagano, T. S., Reitebuch, O., Roca, R., Stoffelen, A., Tucker, S., Wilson, A., Wu, L., & Yanovsky, I. (2024). Vientos – A new satellite mission concept for 3D wind measurements by combining passive water vapor sounders with Doppler wind lidar. Bulletin of the American Meteorological Society (published online ahead of print 2024). https://doi.org/10.1175/BAMS-D-22-0283.1

CW3E Subseasonal Outlook: 16 February 2024

CW3E Subseasonal Outlook: 16 February 2024

February 16, 2024

Click here for a pdf of this information.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Summary provided by J. Wang, C. Castellano, Z. Yang, M. DeFlorio, and J. Kalansky; 16 February 2024

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*Outlook products are considered experimental

CW3E Event Summary: 26 January – 2 February 2024

CW3E Event Summary: 26 January – 2 February 2024

13 February 2024

Click here for a pdf of this information.

Atmospheric Rivers Produce Heavy Precipitation from Alaska to Southern CA

  • A family of atmospheric rivers (ARs) brought heavy precipitation to portions of Alaska, British Columbia, the Pacific Northwest, and California during 26 Jan – 2 Feb.

The ARs:

  • AR #1 made landfall in Oregon on 26 Jan and produced at least 2–6 inches of precipitation in portions of western Washington and Oregon.
  • AR #2 made landfall in British Columbia and southeastern Alaska on 28 Jan and produced 6–12 inches of precipitation over Vancouver Island, the Coast Mountains, the Alaska Panhandle, and the St. Elias Mountains.
  • AR #3 produced AR4 conditions (based on the Ralph et al. 2019 AR Scale) along the southern Oregon coast and AR3 conditions in coastal Northern California.
  • AR #3 brought widespread precipitation to California, including 4–8 inches of rain in the Northern California Coast Ranges and western Transverse Ranges, and 1–3 feet of snow in the Sierra Nevada.
  • All three ARs were fed from a tropical moisture source referred to as a Tropical Moisture Export (TME).

Impacts:

  • Rain falling on moist soils caused minor-to-moderate riverine flooding in western Washington during the first AR.
  • The greatest hydrologic impacts occurred in British Columbia during the second AR, with significant flooding near Pemberton, BC.
  • Minor flooding and several landslides were reported in Northern California during the third AR
  • This family of ARs and nearby essential atmospheric features were sampled by the NOAA and the 53rd Weather Reconnaissance Squadron as part of the AR Recon field campaign.

Click images to see loops of West-WRF IVT/IWV analyses and forecasts

Valid: 0000 UTC 26 January – 0900 UTC 2 February 2024


 

 

 

 

 

 

 

 

 

 

 

 

 

Summary provided by C. Castellano, S. Bartlett, J. Cordeira, P. Iniguez, J. Kalansky, M. Steen, and S. Roj; 13 Feb 2024

To sign up for email alerts when CW3E post new AR updates click here.