A lake ice phenology dataset for the Northern Hemisphere based on passive microwave remote sensing

Figures & data

Figure 1. The distribution of the 753 lakes in the Northern Hemisphere that were the subject of this study. The dark/light blue circles represent different types of data coverage and the dark/light red triangles represent the use of different verification data.

Table 1. Sources and characteristics of PMW data used in this study.

Period of coverage	Sensor	Frequency (GHz)	Spatial Resolution(km×km)	Source
Enhanced data				NSIDC (The Calibrated Passive Microwave Daily EASE-Grid 2.0 data, https://nsidc.org/data/NSIDC-0630/versions/1)
October 1978 to July 1987	SMMR	18.0	6.25 × 6.25 (enhanced resolution)
August 1987 to May 2002	SSM/I	19.35
June 2002 to July 2011	AMSR-E	18.7
L1 data
August 2011 to August 2012	MWRI	18.7	50 × 30	NSMC (http://data.nsmc.org.cn)
September 2012 to September 2020	AMSR2	18.7	22 × 14	JAXA (http://global.jaxa.jp/)

Figure 2. The different components of the lake ice phenology algorithm that was developed in this study.

Figure 3. Time-series of brightness temperatures extracted from the PMW data for the period August 2013 to July 2014 at Hala lake. The four MODIS images illustrate the surface ice coverage corresponding to the FO, CIC, MO and CIF dates.

Figure 4. Multi-seasonal brightness temperature time-series for (a) Kayigyalik lake and (b) the lake Hy_ID555, where it proved difficult to identify some of the ice phenology parameters. The surface areas of these lakes are 139.5 km² and 138.5 km², respectively, and the lakes are located at (162.5 °W, 61.1 °N) and (92.6 °W, 54.5 °N).

Figure 5. Comparison between (a) the CIC and (b) CIF dates identified from the PMW data and the corresponding values from the NSIDC’s GLRIPD.

Figure 6. Verification of the lake ice phenology results: results extracted from MODIS data plotted (y-axis) against results extracted from PMW (x-axis) data for (a) the FO, (b) the CIC, (c) the MO and (d) the CIF dates, respectively.

Table 2. Dataset attribute descriptions.

Table	Parameter	Description
Physical character	This table details the attributes of lakes with monitoring records.
	ID	Unique dataset identifier
	hy_id	The number of the lake in the HydroLAKES database
	Name*	The name of the lake
	Sample center_lat	Sampling point latitude
	Sample center_long	Sampling point longitude
	Area*	Lake surface area in square kilometers
	Altitude*	The elevation of the lake surface in meters
	Vol_total*	The total volume of the lake in millions of cubic meters
	Depth_avg*	The average depth of the lake in meters
	Country*	The country where the lake is located
	Continent*	The continent where the lake is located
	PMW_year	The start and end years for the PMW monitoring
	Ob_year	The start and end years of the ground observation records
	NSIDC_lake code	Lake observation station (from the NSIDC)
	MODIS_Ob	Whether the lake ice extent was obtained from MODIS data: Y = yes, N = no
xxx Lake	lake ice phenology records can be found for the lake with ID xxx
	Season	The ice season given in the form YYYY, where YYYY is the year
	Freeze Onset	Freeze Onset: the date on which the sampling point first freezes – given in YYYY, M, D format, where YYYY is the year, M (1 or 2 digits) is the month and D is the day (1 or 2 digits)
	Complete Ice Cover	Complete Ice Cover: the date on which the sampling point first appears to be completely frozen – given in YYYY, M, D format
	Melt Onset	Melt Onset: the date on which the snow on the surface of the ice begins to melt – given in YYYY, M, D format
	Complete Ice Free	Complete Ice Free: the date on which the sampling point first appears to be completely free of ice – given in YYYY, M, D format

*Records from the HydroLAKES database.

Table 3. Statistics of the lakes in the dataset.

Spatial unit	Number of lakes		Average Area (km^2)	Average depth (m)	Average volume (km^3)	Average elevation (m)	Number of ground stations
	(1978–2020)	(2002–2020)
Size class (km^2)
< 50	38	37	43.93	8.02	0.35	786.68	0
50–100	42	87	68.49	9.57	0.67	1685.55	0
100–500	194	189	250.84	16.36	4.38	870.17	22
500–1000	61	17	715.87	15.97	11.58	547.35	10
> 1000	74	14	4,253.97	31.30	381.70	394.44	22
Continent
Asia	46	106	502.52	14.88	9.91	3,481.35	1
Europe	47	69	1,244.52	20.58	223.45	135.34	21
North America	316	169	654.93	15.37	18.26	293.31	32
Lake data by country
Canada	298	154	619.19	15.72	17.99	296.94	30
China	28	89	272.51	13.49	5.05	4,134.06	1
Russia	34	55	1,420.86	22.14	288.84	143.42	13
United States of America	17	14	1,211.64	8.58	23.04	228.42	2
Finland	10	6	741.16	16.41	8.58	84.38	8
Lake data by latitude range
28.57 °N–35 °N	12	61	223.99	17.07	5.75	4,693.92	0
35 °N–40 °N	10	23	301.08	12.48	5.18	4,421.94	1
40 °N–45 °N	5	9	2,463.17	13.72	41.16	1,262.43	2
45 °N–50 °N	32	34	980.00	12.88	14.55	503.55	2
50 °N–55 °N	74	86	917.41	18.41	161.23	350.74	17
55 °N–60 °N	88	59	558.16	13.87	10.39	261.87	12
60 °N–65 °N	156	52	602.95	16.52	19.84	209.93	14
65 °N–74.5 °N	32	20	1,128.65	18.94	52.01	179.83	6

Figure 7. Spatial patterns in the lake ice phenology results: (a), (d), and (e) show the average ice cover duration, the average FO date, and the average CIF date, respectively, during the period 2000 to 2020. (b) and (c) show statistics for the ice-cover duration by region.

Table 4. Statistics on the number of frozen lakes with areas less than 50 km^2.

Area (km^2)	Asia	Europe	North America	Total number	Total area (km^2)
0.1–1	22.3 × 10^3	225.0 × 10^3	860.9 × 10^3	1,108.2 × 10^3	307.3 × 10^3
1–10	6.7 × 10^3	42.9 × 10^3	95.1 × 10^3	144.7 × 10^3	359.4 × 10^3
10–20	548	1,863	4,433	6,844	94.2 × 10^3
20–30	293	506	1,215	2,014	55.2 × 10^3
30–40	116	250	631	997	34.4 × 10^3
40–50	85	152	357	594	26.5 × 10^3
Total number	30.1 × 10^3	270.7 × 10^3	962.7 × 10^3	1,263.4 × 10^3	NA
Total area (km^2)	50.5 × 10^3	231.4 × 10^3	594.9 × 10^3	NA	876.8 × 10^3

Data availability statement

The dataset is openly available from the repository located at http://www.doi.org/10.11922/sciencedb.j00076.00081.