Greenland Climate Studies: Rain, Snow, or Total?

Use this guide to identify whether a Greenland climate study reports rainfall, snowfall, or total precipitation. You will need the paper, dataset, or chart and, ideally, its methods or metadata; the key is to check definitions, units, and measurement methods rather than infer the quantity from a label alone.

What You’ll Need

• The study, report, dataset, or figure you want to interpret.
• Access to its methods, glossary, supplementary information, or data dictionary, if available.
• A way to note the exact variable name, units, time period, and location shown.

Step-by-Step

1. Find the variable name and its definition. Search the paper or dataset documentation for terms such as “precipitation,” “rain,” “snowfall,” “solid precipitation,” and “liquid precipitation.” Read the definition, not just the chart title or column heading. “Precipitation” often means water falling from the atmosphere in liquid or solid form, but a specific study may define or process it differently. “Snowfall” generally refers to snow that falls; it does not automatically mean the depth of snow on the ground.
2. Check whether the study separates rain and snow. Look for separate variables, such as rainfall and snowfall, or a stated phase classification. If there are two precipitation fields, find out whether each is measured or estimated and whether they are reported in compatible units. A study might classify precipitation by temperature, a model’s phase scheme, or observations. Do not assume every study uses the same threshold or method.
3. Look for an explicit total-precipitation definition. Total precipitation commonly combines liquid and solid precipitation, often expressed as liquid-water equivalent. Confirm that the study says this, or that its metadata identifies the variable as total precipitation. Do not add two fields simply because they are named rain and snow: they may overlap, use different units, or represent different stages of processing.
4. Read the units carefully. Millimetres or kilograms per square metre commonly describe precipitation as water equivalent, especially for snowfall in climate datasets. A centimetre or metre of snow depth describes the depth of accumulated snow, not the amount of water in it. Converting snow depth to water equivalent requires information about snow density; there is no universal fixed conversion. Also distinguish a rate, such as millimetres per day, from an accumulated amount over a month or year.
5. Check the time basis and accumulation period. Determine whether the value is instantaneous, a daily rate, or an accumulation over a specified interval. A variable called “precipitation” may be provided as an amount accumulated since the previous model step, for example. Confirm the timestamps and whether values are reset, averaged, summed, or converted before comparing periods or datasets.
6. Inspect the methods and source of the data. Find out whether the value comes from a gauge, remote sensing, a weather or climate model, or a combination. In Greenland, measurement and estimation methods matter: snowfall can be difficult to measure, and wind can affect gauge catch. A model may estimate rain and snow using its own rules. The method helps explain what the variable represents, but does not by itself prove that it is total precipitation.
7. Check the study’s wording near the result. Read the paragraph, caption, and legend around the number. Phrases such as “rainfall increased” or “snowfall accumulation” may describe a subset or a snow-on-ground outcome, while “precipitation” may refer to both phases. Make sure the authors use the term consistently in the text, figure, and data files.
8. Verify the conclusion against the metadata. Record the study’s exact variable name, definition, units, and period. If the documentation explicitly defines total precipitation as liquid plus solid water equivalent, classify it as total. If it identifies only rain or only snowfall, classify it accordingly. If the definition is missing or ambiguous, label it “unclear” rather than guessing and look for a cited dataset guide or contact information.

Common Mistakes

Taking “precipitation” to mean rain only. In climate research, precipitation can include rain, snow, and sometimes other forms. Check the authors’ definition before interpreting it.

Confusing snow depth with snowfall amount. Snow depth is the snowpack’s height at a location. Snowfall may be measured as fresh-snow depth or as the water equivalent of snow that fell. These are different quantities and can change differently as snow settles or melts.

Assuming a combined value is obvious. A “total” field may be a model output, a sum of components, or a separately processed quantity. Check the stated method. Do not add rain and snow measurements unless their periods, units, and definitions match and the documentation says the sum is appropriate.

Ignoring units or time intervals. An annual total cannot be compared directly with a daily rate. Nor can snow depth be added directly to rainfall in millimetres of water equivalent.

Using temperature alone to classify precipitation. Near-surface temperature can help explain phase, but precipitation phase depends on atmospheric conditions and the study’s classification method. A temperature value does not establish how the dataset labels each event.

Tips

• Search the paper’s supplementary files and the dataset’s data dictionary; variable definitions are often clearer there than in a figure.
• Keep a small record: variable name, rain/snow/total definition, units, accumulation period, and source or method.
• When comparing studies, standardize both the phase definition and water-equivalent basis before drawing conclusions.
• Distinguish precipitation falling from the sky from snowfall accumulation, snowpack change, and surface mass balance. These are related but not interchangeable quantities.
• Use “water equivalent” only when the study or metadata supports it. Do not infer it just from a familiar-looking unit.

Troubleshooting

The chart only says “precipitation.” Find the underlying variable name, methods section, or source dataset. If those do not define the phase, report that the chart does not make it clear; do not call it rainfall by default.

The paper reports rain and snow but gives no total. Check whether both components cover the same grid, period, and water-equivalent units. If they do not, or the processing is unclear, do not calculate a total. State that the study reports separate components.

The unit is unfamiliar or absent. Look up the exact variable in the dataset documentation and check whether the value is a rate, depth, mass per area, or accumulated water equivalent. If the unit cannot be confirmed, avoid numerical comparisons and ask the data provider or authors for clarification.

Different sections seem to contradict each other. Compare the methods, figure caption, and dataset metadata, noting version and period. A paper may discuss total precipitation while a figure shows snowfall alone. If the conflict remains unresolved, describe both statements and identify the ambiguity.

You cannot access the methods or metadata. Search the title, dataset name, variable code, and cited source documentation. If no definition is available, classify the measurement as unknown rather than relying on a headline, map color, or assumed convention.

Frequently Asked Questions

Does “precipitation” include snowfall in Greenland studies?
It often can, but the study’s own definition controls. Check whether solid precipitation is included or reported separately.

Is snowfall in millimetres the depth of snow?
Not necessarily. Millimetres often indicate liquid-water equivalent. Confirm the variable definition; snow depth is a separate measurement.

Can I add rainfall and snowfall to get total precipitation?
Only if the study defines them as compatible, non-overlapping components for the same period and location, with matching units. Otherwise, do not assume the sum is valid.

Does a snowfall measurement mean snow accumulated on the ground?
No. Snowfall describes snow that falls, while snowpack depth or accumulation describes what remains on the surface after effects such as settling and melting.

What if the study never defines its precipitation variable?
Check its cited dataset documentation or ask the authors or data provider. Until clarified, describe the phase as unspecified rather than guessing.

Why might two Greenland studies give different precipitation values?
They may use different observation or model methods, phase definitions, time periods, spatial coverage, or water-equivalent processing. Compare those details before interpreting the difference.

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