Lake Superior North Shore Climate Jim Zandlo State Climatology Office DNR-Waters 2006

Superior Climate snow season Dry summer, low lake

Superior Climate snow season –More-or-less ‘normal’ precipitation spring runoff was (probably) more-or-less ‘normal’ –Snowfall pattern very similar to 4-year SnowRules! result –climate.umn.edu/SnowRules then click on map

A slow start in NE (again) …

Snowfall Dec 13-19, 2005

… right past ‘normal’ snow depth

Snowfall Nov 2005 – Apr 2006

Superior Climate snow season –Snowfall transect updated Fraction of median (was fraction of max) Log-of-distance spreads out values close to Lake Superior –climate.umn.edu/SnowRules then click on map

Superior Climate snow season Dry summer –Low Lake Superior –Basic hydrology GLERL time series

Superior Climate snow season Dry summer –Near record low water levels ( ) on Lake Superior –Basic hydrology Summer is primary recharge period for Lake Superior GLERL time series What happens next?

A range of almost 4 feet in the observational record. Lake Level:

Lake level = old lake level + precipitation on lake + runoff from surrounding land (flow in) - lake evaporation - flow out at outlet (Sault Saint Marie, MI) + / - groundwater flow Basic Lake Hydrology

Geography and General Hydrology - large, ‘state-sized’ watershed - ‘narrow’ along American shore

Water for runoff, cisterns

Water coming in … Runoff 37% Precipitation 59% on lake Diversion 4% …must go out (most of the time) St. Mary’s River 57% Evaporation 43% Deposition 0.2%

Water coming in … Runoff 1.7 ft Precipitation 2.7 ft Diversion 0.2 ft …varies Deposition 0.2% Year ending 11/1985 had 10% more water Year ending Feb 2001 had 15% less water Precipitation 3.1 ft Precipitation 2.6 ft Runoff 1.8 ft Runoff 1.1 ft

Water coming in … Runoff 1.7 ft Precipitation 2.7 ft Diversion 0.2 ft …varies Deposition 0.2% Year ending 11/1985 had 10% more water Year ending Feb 2001 had 15% less water Precipitation 3.1 ft Precipitation 2.6 ft Runoff 1.8 ft Runoff 1.1 ft

Water coming in … Runoff 1.7 ft Precipitation 2.7 ft Diversion 0.2 ft …varies Deposition 0.2% Year ending 11/1985 had 10% more water Year ending Feb 2001 had 15% less water Precipitation 3.1 ft Precipitation 2.6 ft Runoff 1.8 ft Runoff 1.1 ft

Future developments? (What happens next?) Superior Climate

Lake Superior evaporation …

is not the same as evapotranspiration from nearby land surfaces

NOAA Buoys -meteorological parameters -sea measurement -wave info -water temperature -

Lake Evaporation equation Evaporation = factor * D  ‘factor’ varies with weather, surface conditions, etc.  ‘D’ is the difference in vapor pressure between two different air masses If this year’s atmospheric humidity was essentially ‘normal’ (don’t know yet) then using the above equation, evap would have been about 0.5 foot more than ‘normal’ this Aug-Oct.

Lake Evaporation equation September water at 9+°F ’above normal’ has cooled to a little more than 5+°F by Oct 23. The water will tend toward 32°F (and be ‘more normal’) as winter progresses. If water temperature becomes ‘normal’ by mid- winter, an additional 0.2 feet or more than ‘normal’ can be expected to evaporate from the lake this winter.

A range of almost 4 feet in the observational record. Lake Level: Where will it actually end up?

Winter Outlook (a strong ‘el nino’ influence)

Let it snow! Varley

Lake Superior North Shore Climate Jim Zandlo State Climatology Office DNR-Waters 2006 (thermochrons)

Thermochrons, transects Thermochrons, the dime sized devices that measure and store thousands of temperatures, are being used throughout the SnowRules! study area to gather temperatures where the snow falls, namely on snowboards. They are also being used to get air and water temperatures at a few other locations. See the data at climate.umn.edu/SnowRules

f ° F at 5/28/ :00

Let it snow!

Superior Climate snow season Dry summer –Near record low water levels ( ) on Lake Superior –Basic hydrology Summer is primary recharge period for Lake Superior GLERL time series What happens next?

Let it snow!

A range of almost 4 feet in the observational record. Lake Level:

Superior Climate Geography and Hydrology Summarizing the observations –Normal Temperature –Satellite-based measurements –Is it ‘elevation’ or ‘the lake’ –Normal Precipitation –Snowfall patterns –Temperature versus snow

Great Lakes Hydrology (climate) Basin maps: limited detail Balance of incoming/outgoing –Superior evaporation smaller fraction of precipitation than other great lakes Lake levels are ‘integrator’

Cold! Cool Dry

Evapo-transpiration Evapo- transpi- ration

Runoff

A range of almost 4 feet in the observational record. Lake Level:

Hydrology is ‘forced’ by climate How do patterns arise? –‘weather patterns’ –cool/warm water nearby –topography (Water flows downhill) topo  temp  evap  runoff –All the above interacting (!) What do patterns of ‘climate’ variables look like?

Wind – winter transect Inland: mostly N-NW or S-SW Shore: strong tendency to ‘follow’ Can transport air masses across the shoreline Hibbing Grand Marais airport Grand Marais shore

Wind – winter along shore ‘Everywhere’ along shore has strong tendency for ‘along shore’ winds in winter Two Harbors Silver Bay Grand Marais shore

Wind – seasons at Grand Marais Tendency to be ‘along shore’ less in summer

Air moisture (air mass)

Normal Temperature Biggest near shore influences near equinoxes –Land near seasonal extremes –Lake ‘lags’ land by a month or two Detail limited by 25-mile NWS observer spacing winter(DJF) spring(MAM) summer(JJA) fall(SON)

Satellite-based ice observations Most of Minnesota averages less than 2 months. Much of north shore not until Feb ‘ice out’ by early to mid-March

20 years of buoy data at red circle. No mid- winter buoy data is available. Commonly open water in mid-winter means a large wet surface near 32 degrees is often near the north shore anytime during winter.

Land versus ‘sea’ Two Harbors and Grand Marais temps ‘buoyed up’ in winter, ‘anchored’ to lower values in summer. Water maximum lags land maximum.

Land versus ‘sea’ Shore virtually identical in winter to MSP 150 miles south! At Babbitt about 6 F cooler than MSP year-round. Land versus ‘sea’

Temperature is also affected by elevation. Some of the steepest gradients of the Great Lakes are along Minnesota’s north shore.

Thermochrons, transects Thermochrons are dime sized devices that measure and store thousands of temperatures. A contact sensor is later used to download the data.

‘Board’ versus ‘air’

Sea breeze by day …

Land breeze at night

Normal Precipitation Everywhere in Minnesota… –Summer is wettest –Winter is driest North shore ‘bands’ most apparent fall, winter –Warmer lake provides energy and moisture winter(DJF) spring(MAM) summer(JJA) fall(SON)

Snow fraction peak

Tettegouche SP transect

Let it snow!